Geranylgeranyl pyrophosphate synthases

ABSTRACT

The present invention relates a variant polypeptide having geranylgeranyl pyrophosphate synthase activity, which variant polypeptide comprises an amino acid sequence which, when aligned with a geranylgeranyl pyrophosphate synthase comprising the sequence set out in SEQ ID NO: 1, comprises at least one substitution of an amino acid residue corresponding to any of amino acids at positions 92, 100 or 235 said positions being defined with reference to SEQ ID NO: 1 and wherein the variant has one or more modified properties as compared with a reference polypeptide having geranylgeranyl pyrophosphate synthase activity. A variant polypeptide of the invention may be used in a recombinant host for the production of steviol or a steviol glycoside.

FIELD

The present disclosure relates to a variant polypeptide havinggeranylgeranyl pyrophosphate synthase activity and to a nucleic acidcomprising a sequence encoding such a polypeptide. The disclosure alsorelates to a nucleic acid construct comprising the nucleic acid and toan expression vector comprising the nucleic acid or nucleic acidconstruct. Further, the disclosure relates to a recombinant hostcomprising the nucleic acid, a nucleic acid construct or expressionvector. The disclosure also relates to a process for the preparation ofsteviol or a steviol glycoside which comprises fermenting a recombinanthost, to a fermentation broth obtainable by such a process and to asteviol glycoside obtained by a process or obtained from thefermentation broth. In addition, the disclosure relates to a compositioncomprising two or more of the steviol glycosides and to a foodstuff,feed or beverage which comprises the steviol glycoside or composition.Further, the disclosure relates to a method for converting a firststeviol glycoside into a second steviol glycoside and to a method forthe production of a variant polypeptide having geranylgeranylpyrophosphate synthase activity

BACKGROUND

The leaves of the perennial herb, Stevia rebaudiana Bert. accumulatequantities of intensely sweet compounds known as steviol glycosides.Whilst the biological function of these compounds is unclear, they havecommercial significance as alternative high potency sweeteners.

These sweet steviol glycosides have functional and sensory propertiesthat appear to be superior to those of many high potency sweeteners. Inaddition, studies suggest that stevioside can reduce blood glucoselevels in Type II diabetics and can reduce blood pressure in mildlyhypertensive patients.

Steviol glycosides accumulate in Stevia leaves where they may comprisefrom 10 to 20% of the leaf dry weight. Stevioside and rebaudioside A areboth heat and pH stable and suitable for use in carbonated beverages andcan be applied in many other foods. Stevioside is between 110 and 270times sweeter than sucrose, rebaudioside A between 150 and 320 timessweeter than sucrose. In addition, rebaudioside D is also a high-potencyditerpene glycoside sweetener which accumulates in Stevia leaves. It maybe about 200 times sweeter than sucrose. Rebaudioside M is a furtherhigh-potency diterpene glycoside sweetener. It is present in traceamounts in certain stevia variety leaves, but has been suggested to havea superior taste profile. Steviol glycosides have traditionally beenextracted from the Stevia plant. In the Stevia plant, (−)-kaurenoicacid, an intermediate in gibberellic acid (GA) biosynthesis, isconverted into the tetracyclic diterpene steviol, which then proceedsthrough a multi-step glycosylation pathway to form the various steviolglycosides. However, yields may be variable and affected by agricultureand environmental conditions. Also, Stevia cultivation requiressubstantial land area, a long time prior to harvest, intensive labourand additional costs for the extraction and purification of theglycosides.

More recently, interest has grown in producing steviol glycosides usingfermentative processes. WO2013/110673 and WO2015/007748 describemicroorganisms that may be used to produce at least the steviolglycosides rebaudioside A and rebaudioside D.

Further improvement of such microorganisms is desirable in order thathigher amounts of steviol glycosides may be produced and/or additionalor new steviol glycosides and/or higher amounts of specific steviolglycosides and/or mixtures of steviol glycosides having desired ratiosof different steviol glycosides may be produced.

SUMMARY

The present disclosure is based on the identification of variantgeranylgeranyl pyrophosphate synthases. These variants may be used inthe production of recombinant hosts suitable for the production ofsteviol and/or one or more steviol glycosides.

Such recombinant hosts may produce higher amounts of steviol glycosidesas compared with recombinant hosts expressing a non-variantgeranylgeranyl pyrophosphate synthase. Production of higher amounts ofsteviol glycosides may make recovery of steviol glycosides easier.Alternatively or in addition, a higher yield may be obtained.

Accordingly, the disclosure relates to a variant polypeptide havinggeranylgeranyl pyrophosphate synthase activity, which variantpolypeptide comprises an amino acid sequence which, when aligned with ageranylgeranyl pyrophosphate synthase comprising the sequence set out inSEQ ID NO: 1 (the wild type GGS sequence from Yarrowia lipolytica),comprises at least one substitution of an amino acid residuecorresponding to any of amino acids at positions:

92, 100 or 235

said positions being defined with reference to SEQ ID NO: 1 and whereinthe variant has one or more modified properties as compared with areference polypeptide having geranylgeranyl pyrophosphate synthaseactivity.

The disclosure also relates to:

-   -   a variant polypeptide having geranylgeranyl pyrophosphate        synthase activity comprising an amino acid sequence having at        least about 95% sequence identity, at least about 96%, at least        about 97%, at least about 98% or at least about 99% sequence        identity to any one of SEQ ID NOs: 3, 5, 7, 9, 11, 13 or 15;    -   a nucleic acid comprising a sequence encoding a variant        polypeptide as disclosed herein;    -   a nucleic acid construct comprising the nucleic acid as        disclosed herein, operably linked to one or more control        sequences capable of directing the expression of a        geranylgeranyl pyrophosphate synthase in a suitable expression        host;    -   an expression vector comprising a nucleic acid or a nucleic acid        construct as disclosed herein;    -   a recombinant host comprising a nucleic acid, a nucleic acid        construct or an expression vector as disclosed herein;    -   a process for the preparation of steviol or a steviol glycoside        which comprises fermenting a recombinant host as disclosed        herein in a suitable fermentation medium and, optionally,        recovering the steviol or steviol glycoside;    -   a fermentation broth comprising a steviol glycoside obtainable        by the process for the preparation of steviol or steviol        glycoside as disclosed herein;    -   a steviol glycoside obtained by a process for the preparation of        steviol or steviol glycoside as disclosed herein or obtained        from a fermentation broth comprising a steviol glycoside as        disclosed herein;    -   a composition comprising two or more steviol glycosides obtained        by a process for the preparation of steviol or steviol glycoside        as disclosed herein or obtained from a fermentation broth        comprising a steviol glycoside as disclosed herein;    -   a foodstuff, feed or beverage which comprises a steviol        glycoside obtained by a process for the preparation of steviol        or steviol glycoside as disclosed herein or obtained from a        fermentation broth comprising a steviol glycoside as disclosed        herein or a food stuff, feed or beverage which comprises a        composition as disclosed herein;    -   a method for converting a first steviol glycoside into a second        steviol glycoside, which method comprises:        -   contacting said first steviol glycoside with a recombinant            host as disclosed herein, a cell free extract derived from            such a recombinant host or an enzyme preparation derived            from either thereof;        -   thereby to convert the first steviol glycoside into the            second steviol glycoside; and    -   a method for producing a geranylgeranyl pyrophosphate synthase        comprising cultivating a host cell as disclosed herein under        conditions suitable for production of the geranylgeranyl        pyrophosphate synthase and, optionally, recovering the        geranylgeranyl pyrophosphate synthase.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 sets out a schematic diagram of the potential pathways leading tobiosynthesis of steviol glycosides.

DESCRIPTION OF THE SEQUENCE LISTING

A description of the sequences is set out in Table 1.

TABLE 1 Description SEQ ID NO Yarrowia lipolytica GGPS SEQ ID NO: 1 CDSYarrowia lipolytica GGPS SEQ ID NO: 2 Yarrowia lipolytica GGPS withGly92Glu SEQ ID NO: 3 mutation CDS Yarrowia lipolytica GGPS withGly92Glu SEQ ID NO: 4 mutation Yarrowia lipolytica GGPS with Ala100ValSEQ ID NO: 5 mutation CDS Yarrowia lipolytica GGPS with Ala100Val SEQ IDNO: 6 mutation Yarrowia lipolytica GGPS with Ser235Asn SEQ ID NO: 7mutation CDS Yarrowia lipolytica GGPS with Ser235Asn SEQ ID NO: 8mutation Yarrowia lipolytica GGPS with Gly92Glu + SEQ ID NO: 9 Ala100Valmutation CDS Yarrowia lipolytica GGPS with Gly92Glu + SEQ ID NO: 10Ala100Val mutation Yarrowia lipolytica GGPS with Gly92Glu + SEQ ID NO:11 Ser235Asn mutation CDS Yarrowia lipolytica GGPS with Gly92Glu + SEQID NO: 12 Ser235Asn mutation Yarrowia lipolytica GGPS with Ala100Val +SEQ ID NO: 13 Ser235Asn mutation CDS Yarrowia lipolytica GGPS withAla100Val + SEQ ID NO: 14 Ser235Asn mutation Yarrowia lipolytica GGPSwith Gly92Glu + SEQ ID NO: 15 Ala100Val + Ser235Asn mutation CDSYarrowia lipolytica GGPS with Gly92Glu + SEQ ID NO: 16 Ala100Val +Ser235Asn mutation Mucor circinelloides GGPS SEQ ID NO: 17 Yarrowialipolytica GGPS with Gly92Asp SEQ ID NO: 18 mutation Yarrowia lipolyticaGGPS with Gly92Asn SEQ ID NO: 19 mutation Yarrowia lipolytica GGPS withGly92Gln SEQ ID NO: 20 mutation Yarrowia lipolytica GGPS with Ala100GlySEQ ID NO: 21 mutation Yarrowia lipolytica GGPS with Ala100Phe SEQ IDNO: 22 mutation Yarrowia lipolytica GGPS with Ala100Tyr SEQ ID NO: 23mutation Yarrowia lipolytica GGPS with Ala100Ile SEQ ID NO: 24 mutationYarrowia lipolytica GGPS with Ala100Leu SEQ ID NO: 25 mutation Yarrowialipolytica GGPS with Ser235Ala SEQ ID NO: 26 mutation Yarrowialipolytica GGPS with Ser235Gly SEQ ID NO: 27 mutation Yarrowialipolytica GGPS with Ser235Gln SEQ ID NO: 28 mutation Yarrowialipolytica GGPS with Ser235Val SEQ ID NO: 29 mutation Yarrowialipolytica GGPS with Ser235Asp SEQ ID NO: 30 mutation Yarrowialipolytica GGPS with Ser235Glu SEQ ID NO: 31 mutation Yarrowialipolytica GGPS with Ser235Phe SEQ ID NO: 32 mutation Yarrowialipolytica GGPS with Ser235Tyr SEQ ID NO: 33 mutation

DETAILED DESCRIPTION

Throughout the present specification and the accompanying claims, thewords “comprise”, “include” and “having” and variations such as“comprises”, “comprising”, “includes” and “including” are to beinterpreted inclusively. That is, these words are intended to convey thepossible inclusion of other elements or integers not specificallyrecited, where the context allows.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e. to one or at least one) of the grammatical object of thearticle. By way of example, “an element” may mean one element or morethan one element.

Herein, “rebaudioside” may be shortened to “reb”. That is to say,rebaudioside A and reb A, for example, are intended to indicate the samemolecule.

The disclosure concerns new polypeptides having geranylgeranylpyrophosphate synthase activity. Recombinant hosts expressing such apolypeptide, i.e. a host cell comprising a recombinant sequence encodingsuch a polypeptide, may be used for the production of steviolglycosides. The ability of a given recombinant host to produce a steviolglycoside may be a property of the host in non-recombinant form or maybe a result of the introduction of one or more recombinant nucleic acidsequences (i.e. encoding enzymes leading to the production of a steviolglycoside). A recombinant host as disclosed herein may be capable ofincreased production of a steviol glycoside in comparison to anon-recombinant host or a recombinant host capable of expressing areference polypeptide having geranylgeranyl pyrophosphate synthaseactivity.

According to the present disclosure, there is thus provided a variantpolypeptide having geranylgeranyl pyrophosphate synthase activity.

A variant polypeptide according to the disclosure has geranylgeranylpyrophosphate synthase activity. Geranylgeranyl pyrophosphate synthase(or geranylgeranyl diphosphate synthase activity) is a term well knownto the skilled person.

For the purpose of this disclosure, a polypeptide having geranylgeranylpyrophosphate synthase (or synthetase) activity is typically one whichcatalyzes the synthesis of GGPP from farnesyl diphosphate andisopentenyl diphosphate.

Geranylgeranyl pyrophosphate synthase activity may also be referred toas GGPP synthase activity, GGPP synthetase activity, GGPPS activity,GGPS activity, GGS activity, GGS1 activity, GGPS1 activity or GGPPS1activity.

Geranylgeranyl pyrophosphate synthase activity may also be defined interms of activity of the product of the carG gene of Mucorcircinelloides. The product of the carG gene of Mucor circinelloides maycatalyze one or more of:

-   -   dimethylallyl diphosphate+isopentenyl        diphosphate=diphosphate+geranyl diphosphate; geranyl        diphosphate+isopentenyl diphosphate=diphosphate+(2E,6E)-farnesyl        diphosphate; or- (2E,6E)-farnesyl diphosphate+isopentenyl        diphosphate=diphosphate+geranylgeranyl diphosphate.

Any of these catalytic activities may be used to define a geranylgeranylpyrophosphate synthase of the disclosure.

Thus, for the purposes of the present disclosure, a polypeptide havinggeranylgeranyl pyrophosphate synthase activity may be one which iscapable of catalysing or partially catalyzing the formation ofgeranylgeranyl pyrophosphate.

A variant polypeptide as disclosed herein has modified geranylgeranylpyrophosphate synthase activity as compared with a reference polypeptidehaving geranylgeranyl pyrophosphate synthase activity.

Such a variant polypeptide may have a decreased specific geranylgeranylpyrophosphate synthase activity as compared with the referencepolypeptide.

Such a variant polypeptide may have an increased specific geranylgeranylpyrophosphate synthase activity as compared with the referencepolypeptide.

A variant polypeptide according to the disclosure may be a non-naturallyoccurring polypeptide.

Herein, variant polypeptides of the disclosure may be referred to as a“geranylgeranyl pyrophosphate synthase variant”, “GGPS” or “GGS”, “GGPSvariant”, “GGS variant”, “variant polypeptide” or “GGPS polypeptide” or“GGS polypeptide” or the like.

A GGPS variant polypeptide having geranylgeranyl pyrophosphate synthaseactivity as disclosed herein may be a variant of a reference polypeptidehaving geranylgeranyl pyrophosphate synthase activity which variantpolypeptide comprises an amino acid sequence which, when aligned with ageranylgeranyl pyrophosphate synthase comprising the sequence set out inSEQ ID NO: 1, comprises at least one substitution of an amino acidresidue corresponding to any of amino acids at positions

92, 100 or 235,

said positions being defined with reference to SEQ ID NO: 1.

A GGPS variant polypeptide as disclosed herein (for example a varianthaving one or more substitution as set out herein) may have at leastabout 60%, 70%, 80% identity with the reference GGPS polypeptide, suchas the GGPS of SEQ ID NO: 1, for example at least about 85% identitywith the reference polypeptide, such as at least about 90% identity withthe reference polypeptide, at least about 95% identity with thereference polypeptide, at least about 98% identity with the referencepolypeptide or at least about 99% identity with the referencepolypeptide. Such a variant will typically have one or more substitutionor sets of substitutions selected from a position corresponding to

92, 100 or 235

as defined with reference to SEQ ID NO: 1.

A GGPS variant polypeptide as disclosed herein may be a variant of thepolypeptide set out in SEQ ID NO: 1, having a substitution at one ormore of positions 92, 100 or 235.

An amino acid position corresponding to one of the positions definedherein in the reference GGPS may be a position that aligns in a multiple(protein) sequence alignment with any of the stated amino acidpositions.

Accordingly, a GGPS variant polypeptide as disclosed herein may be avariant of the polypeptide set out in SEQ ID NO: 17 having asubstitution at one or more of positions 89, 97 or 225.

The inventors have surprisingly found that recombinant host cellsexpressing a variant polypeptide as disclosed herein and having asubstitution at one or more of positions 92, 100 or 235, when used inmethods for producing steviol glycosides, produced significantly highertiters of steviol glycosides and KA-glycosides compared to recombinanthost cells expressing the reference polypeptide.

Two of the three positions where the substitutions according to thepresent disclosure may occur i.e. 92 and 100, respectively, as definedwith reference to SEQ ID NO: 1, are expected to be located in a hingepoint on top of an alpha helix (position 92) and in an alpha-helix(position 100), respectively, that are expected to be located in theprotein homo dimer interphase. A phylogenetic analysis indicated thatpositions homologous to glycine 92 are highly conserved. Without beingbound by a theory, the inventors believe that the surprising resultsobserved might be due to the fact that the mutation of the strictlyconserved glycine 92 to e.g. glutamic acid is likely to have an effecton protein structure and potentially dimer interaction. In phylogeny,little amino acid variation has been observed at positions homologous toA100 but amino acid variation to larger hydrophobic residues like valinehas not been observed. Without being bound by a theory, the inventorsbelieve that the surprising results observed in the examples might bedue to the fact that the Ala100Val mutation might have an effect on thedimer interphase and affect the active site and catalysis by stericinteraction with a neighboring alpha-helix that is part of the substratebinding pocket.

The third position where a mutation may occur, i.e. 235, might belocated in an alpha-helix that is remote from the two positionsdescribed earlier and not involved in protein-protein interactions.Phylogenetic analysis indicated that serine occurs at positionhomologous to Ser235 but that alanine is the most predominant amino acidat this position.

A GGPS variant of the disclosure will typically retain GGPS activity.That is to say, a GGPS variant according to the disclosure willtypically be capable of catalysing the reaction set out above, albeitwith a modified activity as compared with a reference polypeptide.

A suitable reference polypeptide may be a polypeptide comprising theamino acid sequence of SEQ ID NO: 1 (Yarrowia lipolytica), SEQ ID NO: 17(Mucor circinelloides) or the amino acid sequence of a GGPS from S.cerevisiae.

Preferably, a GGPS variant polypeptide according to the disclosure willtypically exhibit improved properties in comparison with the referencepolypeptide from which it is derived, typically in terms of specificactivity and/or substrate specificity. Such an improved property willtypically be one which is relevant if the variant were to be used as setout below, for example in a method for the production of steviol and/ora steviol glycoside (by expressing the GGPS in a recombinant host).

Thus, a GGPS variant according to the disclosure is one which istypically capable of increasing production of steviol and/or a steviolglycoside in a recombinant host capable of the production of saidsteviol and/or a steviol glycoside (in comparison with a recombinanthost capable of the production of steviol and/or a steviol glycosidewhich expresses the reference polypeptide). That is to say,overexpression of a GGPS variant polypeptide according to the disclosurein a host cell will typically lead to increased production of stevioland/or a steviol glycoside as compared to a host cell whichoverexpresses a reference polypeptide (such as the GGPS of SEQ ID NO: 1or SEQ ID NO: 17).

A GGPS variant which exhibits a property which is improved in relationto the reference GGPS is one which demonstrates a measurable reductionor increase in the relevant property, for example specific activity,typically such that the GGPS variant is more suited to a use as set outherein, for example in a method for the production of steviol or asteviol glycoside.

A GGPS variant polypeptide comprises an amino acid sequence that has oneor more substitution, deletion and/or insertion of an amino acid ascompared to the reference polypeptide and/or one or more truncations ascompared to the reference polypeptide. A GGPS variant polypeptide maycomprise one or more of the substitutions described herein.

-   -   A variant polypeptide having GGPS activity, for example as set        out herein, which variant polypeptide has an amino acid sequence        which, when aligned with the GGPS comprising the sequence set        out in SEQ ID NO: 1, comprises at least one substitution of an        amino acid residue corresponding to any of amino acids 92, 100        or 235

said positions being defined with reference to SEQ ID NO: 1 and whereinthe variant has one or more modified properties as compared with areference polypeptide having GGPS activity.

Thus, the amino acid present at one or more of the said positions willbe replaced with a different amino acid than appears at that position inthe reference sequence (the positions being defined with reference toSEQ ID NO: 1).

A variant GGPS according to the disclosure may comprise one of thesubstitutions set out above. However, a variant polypeptide may compriseany combination of substitutions at positions 92, 100 or 235, saidpositions being defined with reference to a suitable reference sequencesuch as that set out in SEQ ID NO: 1, such as two of the substitutionsor all of the substitutions at the said positions.

A variant GGPS may comprise a substitution at position 92 as definedwith reference to SEQ ID NO: 1. The substitution may be such that anamino acid residue selected from a Glu residue, an Asp residue, an Asnresidue, a Gln residue, preferably a Glu residue, is at this position.

Therefore, in one embodiment the variant polypeptide having GGPSactivity as disclosed herein comprises an amino acid sequence which,when aligned with a geranylgeranyl pyrophosphate synthase comprising thesequence set out in SEQ ID NO: 1, comprises a substitution of the aminoacid residue corresponding to amino acid at position 92 with an aminoacid residue selected from a Glu residue, an Asp residue, an Asnresidue, a Gln residue, preferably with a Glu residue, said positionsbeing defined with reference to SEQ ID NO: 1 and wherein the variant hasone or more modified properties as compared with a reference polypeptidehaving geranylgeranyl pyrophosphate synthase activity.

A variant GGPS may comprise a substitution at position 100 as definedwith reference to SEQ ID NO: 1. The substitution may be such that a Valresidue, a Gly residue, a Phe residue, a Tyr residue, a Ile residue, aLeu residue, preferably a Val residue is at this position.

Therefore, in one embodiment the variant polypeptide having GGPSactivity as disclosed herein comprises an amino acid sequence which,when aligned with a geranylgeranyl pyrophosphate synthase comprising thesequence set out in SEQ ID NO: 1, comprises a substitution of the aminoacid residue corresponding to amino acid at position 100 with an aminoacid residue selected from a Val residue, a Gly residue, a Phe residue,a Tyr residue, a Ile residue, a Leu residue, preferably a Val residue,said positions being defined with reference to SEQ ID NO: 1 and whereinthe variant has one or more modified properties as compared with areference polypeptide having geranylgeranyl pyrophosphate synthaseactivity.

A variant GGPS may comprise a substitution at position 235 as definedwith reference to SEQ ID NO: 1. The substitution may be such that a Asnresidue, a Ala residue, a Gly residue, a Gln residue, a Val residue, aAsp residue, a Glu residue, a Phe residue, a Tyr residue, preferably aAsn residue, is at this position.

Therefore, in one embodiment the variant polypeptide having GGPSactivity as disclosed herein comprises an amino acid sequence which,when aligned with a geranylgeranyl pyrophosphate synthase comprising thesequence set out in SEQ ID NO: 1, comprises a substitution of the aminoacid residue corresponding to amino acid at position 235 with an aminoacid residue selected from a Asn residue, a Ala residue, a Gly residue,a Gln residue, a Val residue, a Asp residue, a Glu residue, a Pheresidue, a Tyr residue, preferably a Asn residue, said positions beingdefined with reference to SEQ ID NO: 1 and wherein the variant has oneor more modified properties as compared with a reference polypeptidehaving geranylgeranyl pyrophosphate synthase activity.

A variant GGPS may comprise a substitution at positions 92 and 100 asdefined with reference to SEQ ID NO: 1. The substitutions may be suchthat a Glu and a Val residue are at these positions respectively. Inother embodiments, the substitutions may be such that a Glu and a Gly,or a Glu and a Phe, or a Glu and a Tyr, or a Glu and a Ile, or a Glu anda Leu are at these positions respectively. In other embodiments, thesubstitution at position 92 and 100 as defined with reference to SEQ IDNO: 1 may be such that a Asp and a Val are at these positionrespectively, or a Asp and a Gly, or a Asp and a Phe, or a Asp and aTyr, or a Asp and a Ile, or a Asp and a Leu, or a Asn and a Val, or aAsn and a Gly, or a Asn and a Phe, or a Asn and a Tyr, or a Asn and aIle, or a Asn and a Leu, or a Gln and a Val, or a Gln and a Gly, or aGln and a Phe, or a Gln and a Tyr, or a Gln and a Ile, or a Gln and aLeu are at these positions.

A variant GGPS may comprise a substitution at positions 92 and 235 asdefined with reference to SEQ ID NO: 1. The substitutions may be suchthat a Glu and a Asn residue are at these positions respectively. Inother embodiments, the substitutions may be such that a Glu and a Ala,or a Glu and a Gly, or a Glu and a Gln, or a Glu and a Val, or a Glu anda Asp, or a Glu and a Glu, or a Glu and a Phe, or a Glu and a Tyr are atthese positions respectively. In other embodiments, the substitution atposition 92 and 235 as defined with reference to SEQ ID NO: 1 may besuch that a Asp and a Asn, or a Asp and a Ala, or a Asp and a Gly, or aAsp and a Gln, or a Asp and a Val, or a Asp and a Asp, or a Asp and aGlu or a Asp and a Phe, or a Asp and a Tyr, or a Asn and a Asn, or a Asnand a Ala, or a Asn and a Gly, or a Asn and a Gln, or a Asn and a Val,or a Asn and a Asp, or a Asn and a Glu, or a Asn and a Phe, or a Asn anda Tyr, or a Gln and a Asn, or a Gln and a Ala, or a Gln and a Gly, or aGln and a Gln, or a Gln and a Val, or a Gln and a Asp, or a Gln and aGlu, or a Gln and a Phe, or a Gln and a Tyr are at these positions.

A variant GGPS may comprise a substitution at positions 100 and 235 asdefined with reference to SEQ ID NO: 1. The substitutions may be suchthat a Val and a Asn residue are at these positions respectively. Inother embodiments, the substitutions may be such that a Val and a Ala,or a Val and a Gly, or a Val and a Gln, or a Val and a Val, or a Val anda Asp, or a Val and a Glu, or a Val and a Phe, or a Val and a Tyr are atthese positions respectively. In other embodiments, the substitutionsmay be such that a Gly and a Asn, or a Gly and a Ala, or a Gly and aGly, or a Gly and a Gln, or a Gly and a Val, or a Gly and a Asp, or aGly and a Glu, or a Gly and a Phe, or a Gly and a Tyr are at thesepositions respectively. In other embodiments, the substitution atposition 100 and 235 as defined with reference to SEQ ID NO: 1 may besuch that a Phe and a Asn, or a Phe and a Ala, or a Phe and a Gly, or aPhe and a Gln, or a Phe and a Val, or a Phe and a Asp, or a Phe and aGlu, or a Phe and a Phe, or a Phe and a Tyr, or a Tyr and a Asn, or aTyr and a Ala, or a Tyr and a Gly, or a Tyr and a Gln, or a Tyr and aVal, or a Tyr and a Asp, or a Tyr and a Glu, or a Tyr and a Phe, or aTyr and a Tyr, or a Ile and a Asn, or a Ile and a Ala, or a Ile and aGly, or a Ile and a Gln, or a Ile and a Val, or a Ile and a Asp, or aIle and a Glu, or a Ile and a Phe, or a Ile and a Tyr, or a Leu and aAsn, or a Leu and a Ala, or a Leu and a Gly, or a Leu and a Gln, or aLeu and a Val, or a Leu and a Asp, or a Leu and a Glu, or a Leu and aPhe, or a Leu and a Tyr are at these positions.

A variant GGPS may comprise a substitution at positions 92, 100 and 235as defined with reference to SEQ ID NO: 1. The substitutions may be suchthat a Glu, a Val and a Asn residue are at these positions respectively.According to embodiments of the disclosure, the combinations ofsubstitutions which may be found in the polypeptide variants accordingto the present disclosure at position 92, 100 and 235 as defined withreference to SEQ ID NO: 1, respectively are as those indicatedhereafter:

each one of 92E+100V or 92E+100G or 92E+100F or 92E+100Y or 92E+1001 or92E+100L or 92D+100V or 92D+100G or 92D+100F or 92D+100Y or 92D+1001 or92D+100L or 92N+100V or 92N+100G or 92N+100F or 92N+100Y or 92N+1001 or92N+100L or 92Q+100V or 92Q+100G or 92Q+100F or 92Q+100Y or 92Q+100I or92Q+100L, respectively, combined with each one of N, A; G, Q; V; D, E;F; or Y at position 235, respectively; or

each one of 92E+235N or 92E+235A or 92E+235G or 92E+235Q or 92E+235V or92E+235D or 92E+235E or 92E+235F or 92E+235Y or 92D+235N or 92D+235A or92D+235G or 92D+235Q or 92D+235V or 92D+235D or 92D+235E or 92D+235F or92D+235Y or 92N+235N or 92N+235A or 92N+235G or 92N+235Q or 92N+235V or92N+235D or 92N+235E or 92N+235F or 92N+235Y or 92Q+235N or 92Q+235A or92Q+235G or 92Q+235Q or 92Q+235V or 92Q+235D or 92Q+235E or 92Q+235F or92Q+235Y, respectively, combined with each one of V, G, F, Y, I, L atposition 100, respectively; or

each one of 100V+235N or 100V+235A or 100V+235G or 100V+235Q or100V+235V or 100V+235D or 100V+235E or 100V+235F or 100V+235Y or100G+235N or 100G+235A or 100G+235G or 100G+235Q or 100G+235V or100G+235D or 100G+235E or 100G+235F or 100G+235Y or 100F+235N or100F+235A or 100F+235G or 100F+235Q or 100F+235V or 100F+235D or100F+235E or 100F+235F or 100F+235Y or 100Y+235N or 100Y+235A or100Y+235G or 100Y+235Q or 100Y+235V or 100Y+235D or 100Y+235E or100Y+235F or 100Y+235Y or 100I+235N or 100I+235A or 100I+235G or100I+235Q or 100I+235V or 100I+235D or 100I+235E or 100I+235F or100I+235Y or 100L+235N or 100L+235A or 100L+235G or 100L+235Q or100L+235V or 100L+235D or 100L+235E or 100L+235F or 100L+235Y,respectively, combined with each one of E, D, N, or Q at position 92,respectively.

A GGPS variant polypeptide of the disclosure may be a variant of thepolypeptide set out in SEQ ID NO: 17 having a substitution at one ormore of positions 89, 97 or 225 of that sequence. Thus, a variant of thedisclosure may comprise: substitutions at positions 89 and 97;substitutions at positions 89 and 225; substitutions at positions 97 and225; or substitutions at positions 89, 97, 225. Preferred substitutionsare one or more of Glu, Asp, Asn, or Gln, preferably Glu at position 89,Val, Gly, Phe, Tyr, Ile, or Leu, preferably Val at position 97 and Asn,Ala, Gly, Gln, Val, Asp, Glu, Phe, or Tyr, preferably Asn at position225.

A variant polypeptide of the disclosure may comprise additionalsubstitutions other than the three positions defined above, for example,one or more additional substitutions, additions or deletions.

A variant of the disclosure may comprise a combination of differenttypes of modification of this sort. A variant may comprise one, two,three, four, at least 5, at least 10, at least 15, at least 20, at least25, at least 30 or more such modifications (which may all be of the sametype or may be different types of modification). Typically, theadditional modifications may be substitutions.

Such additional modifications may occur in the hinge region and/or thealpha-helix region referred to above.

A variant polypeptide of the disclosure may comprise the amino acidsequence set out in SEQ ID NOs: 3, 5, 7, 9, 11, 13, 15, or 18 to 33.

A host cell of the disclosure may comprise nucleic acids encoding one,two, three, four, five or more variants of the disclosure. Such variantsmay be the same or different. A host cell may comprise a nucleic acidencoding the GGPS of SEQ ID NO: 1 and a nucleic acid encoding one ormore variants of the disclosure. That is to say, a host cell maycomprise a nucleic acid encoding the GGPS of SEQ ID NO: 1 and a nucleicacid encoding one or more variants of the disclosure, each of which maybe present in a copy of one, two, three, four, five or more.

A variant polypeptide will typically have modified GGPS activity incomparison to a reference polypeptide. Typically, the modified activitymay be defined in terms of steviol and/or steviol glycoside productionin a recombinant host.

The modified activity may be defined in terms of an increase in theproduction of steviol and/or a steviol glycoside when a variant GGPS isoverexpressed in a host cell as compared to the production level of anequivalent host cell which overexpresses a reference polypeptide, forexample that of SEQ ID NO: 1 or SEQ ID NO: 17.

The modified activity may be defined in terms of a change in ratio ofthe production of two steviol glycosides, for example the ratio ofrebaudioside A: rebaudioside M may be increased or, alternatively, theratio of rebaudioside M: rebaudioside A may be increased, when a variantGGPS is overexpressed in a host cell as compared to the production levelof an equivalent host cell which overexpresses a reference polypeptide,for example that of SEQ ID NO: 1 or SEQ ID NO: 17.

A variant GGPS may be capable of increasing production levels, forexample by at least 5%, at least 10%, at least 25%, at least 50%, atleast 100% or more. Production levels may be expressed in terms of g/Lor mol/L (M), so an increase in the production level of steviol and/orsteviol glycosides will be evident by higher level of production interms of g/L or mol/L.

The word “polypeptide” is used herein for chains containing more thanabout seven amino acid residues. All polypeptide sequences herein arewritten from left to right and in the direction from amino terminus tocarboxy terminus. The one-letter code of amino acids used herein iscommonly known in the art and can be found in Sambrook, et al.(Molecular Cloning: A Laboratory Manual, 2nd ed. Cold Spring HarborLaboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor,N.Y., 1989).

A GGPS variant polypeptide as disclosed herein may be in isolated form,such as substantially isolated form. By “isolated” polypeptide orprotein is intended a polypeptide or protein removed from its nativeenvironment. For example, recombinantly produced polypeptides andproteins expressed in host cells are considered isolated for the purposeof the disclosure as are recombinant polypeptides which have beensubstantially purified by any suitable technique. A GGPS variantpolypeptide according to the disclosure can be recovered and purifiedfrom recombinant cell cultures by methods known in the art.

GGPS variant polypeptides of the present disclosure include products ofchemical synthetic procedures, and products produced by recombinanttechniques from a prokaryotic or eukaryotic host, including, forexample, bacterial, yeast, higher plant, insect and mammalian cells.Depending upon the host employed in a recombinant production procedure,the polypeptides of the present disclosure may be glycosylated or may benon-glycosylated. In addition, polypeptides of the disclosure may alsoinclude an initial modified methionine residue, in some cases as aresult of host-mediated processes.

The present disclosure also features biologically active fragments ofthe GGPS polypeptide variants according to the disclosure. Suchfragments are considered to be encompassed within the term “a GGPSvariant according to the disclosure”.

Biologically active fragments of a GGPS polypeptide variant includepolypeptides comprising amino acid sequences sufficiently identical toor derived from the amino acid sequence of a variant protein asdisclosed herein which include fewer amino acids than the full-lengthprotein but which exhibit at least one biological activity of thecorresponding full-length protein. Typically, biologically activefragments comprise a domain or motif with at least one activity of avariant protein as disclosed herein. A biologically active fragment of aGGPS variant according to the disclosure can be a polypeptide which is,for example, 10, 25, 50, 100 or more amino acids in length. Moreover,other biologically active portions, in which other regions of theprotein are deleted, can be prepared by recombinant techniques andevaluated for one or more of the biological activities of the nativeform of a polypeptide according to the disclosure.

Typically, a protein fragment of a GGPS variant as disclosed herein willcomprise one or more of the substitutions defined herein.

The disclosure also features nucleic acid fragments which encode theabove biologically active fragments (which biologically active fragmentsare themselves variants of the disclosure).

The present disclosure provides polynucleotides which comprise asequence encoding a GGPS variant polypeptide as disclosed herein (andbiologically active fragments thereof). The disclosure also relates toan isolated polynucleotide encoding at least one functional domain of aGGPS polypeptide variant as disclosed herein. Typically, such a domainwill comprise one or more of the substitutions described herein.

A nucleic acid molecule as disclosed herein can be generated usingstandard molecular biology techniques well known to those skilled in theart taken in combination with the sequence information provided herein.For example, using standard synthetic techniques, the required nucleicacid molecule may be generated by PCR or synthesized de novo. Such asynthetic process will typically be an automated process.

A nucleic acid as disclosed herein may comprise one or more deletions,i.e. gaps, in comparison to a nucleic acid encoding a reference GGPS.Such deletions/gaps may also be generated using site-directedmutagenesis using appropriate oligonucleotides. Techniques forgenerating such deletions are well known to those skilled in the art.

Furthermore, oligonucleotides corresponding to or hybridizable tonucleotide sequences according to the disclosure can be prepared bystandard synthetic techniques, e.g., using an automated DNA synthesizer.

Also, complementary nucleic acids and antisense nucleic acids areincluded in the present disclosure. A nucleic acid molecule which iscomplementary to another nucleotide sequence is one which issufficiently complementary to the other nucleotide sequence such that itcan hybridize to the other nucleotide sequence thereby forming a stableduplex.

One aspect of the disclosure pertains to isolated nucleic acid moleculesthat encode a variant polypeptide of the invention, or a biologicallyactive fragment or domain thereof, as well as nucleic acid moleculessufficient for use as hybridization probes to identify nucleic acidmolecules encoding a polypeptide as disclosed herein and fragments ofsuch nucleic acid molecules suitable for use as PCR primers for theamplification or mutation of nucleic acid molecules, such as for thepreparation of nucleic acid molecules of the disclosure.

An “isolated nucleic acid” or “isolated polynucleotide” is a DNA or RNAthat is not immediately contiguous with both of the coding sequenceswith which it is immediately contiguous (one on the 5′ end and one onthe 3′ end) in the naturally occurring genome of the organism from whichit is derived. Thus, in one embodiment, an isolated nucleic acidincludes some or all of the 5′ non-coding (e.g., promotor) sequencesthat are immediately contiguous to the coding sequence. The termtherefore includes, for example, a recombinant DNA that is incorporatedinto a vector, into an autonomously replicating plasmid or virus, orinto the genomic DNA of a prokaryote or eukaryote, or which exists as aseparate molecule (e.g., a cDNA or a genomic DNA fragment produced byPCR or restriction endonuclease treatment) independent of othersequences. It also includes a recombinant DNA that is part of a hybridgene encoding an additional polypeptide that is substantially free ofcellular material, viral material, or culture medium (when produced byrecombinant DNA techniques), or chemical precursors or other chemicals(when chemically synthesized). Moreover, an “isolated nucleic acidfragment” is a nucleic acid fragment that is not naturally occurring asa fragment and would not be found in the natural state.

As used herein, the terms “nucleic acid”, “polynucleotide” or “nucleicacid molecule” are intended to include DNA molecules (e.g., cDNA orgenomic DNA) and RNA molecules (e.g., mRNA) and analogs of the DNA orRNA generated using nucleotide analogs. The nucleic acid molecule can besingle-stranded or double-stranded, but preferably is double-strandedDNA. The nucleic acid may be synthesized using oligonucleotide analogsor derivatives (e.g., inosine or phosphorothioate nucleotides). Sucholigonucleotides can be used, for example, to prepare nucleic acids thathave altered base-pairing abilities or increased resistance tonucleases.

The disclosure also relates to a nucleic acid construct comprising apolynucleotide sequence encoding a variant polypeptide according to thedisclosure and, linked operably thereto, control sequences permittingexpression of the polynucleotide sequence in a host cell. The nucleicacid construct may be incorporated into a vector, such as an expressionvector and/or into a host cell in order to effect expression of thevariant polypeptide.

The term “nucleic acid construct” is herein referred to as a nucleicacid molecule, either single-or double-stranded, which is isolated froma naturally-occurring gene or, more typically, which has been modifiedto contain segments of nucleic acid which are combined and juxtaposed ina manner which would not otherwise exist in nature. The term nucleicacid construct is synonymous with the term “expression cassette” whenthe nucleic acid construct contains all the control sequences requiredfor expression of a coding sequence, wherein said control sequences areoperably linked to said coding sequence.

As used herein, the term “operably linked” refers to a linkage ofpolynucleotide elements (or coding sequences or nucleic acid sequence)in a functional relationship. A nucleic acid sequence is “operablylinked” when it is placed into a functional relationship with anothernucleic acid sequence. For instance, a promoter or enhancer is operablylinked to a coding sequence if it affects the transcription of thecoding sequence.

As used herein, the term “promoter” refers to a nucleic acid fragmentthat functions to control the transcription of one or more genes,located upstream with respect to the direction of transcription of thetranscription initiation site of the gene, and is structurallyidentified by the presence of a binding site for DNA-dependent RNApolymerase, transcription initiation sites and any other DNA sequencesknown to one of skilled in the art. A “constitutive” promoter is apromoter that is active under most environmental and developmentalconditions. An “inducible” promoter is a promoter that is active underenvironmental or developmental regulation.

A promoter that could be used to achieve the expression of a nucleotidesequence coding for an enzyme such as a variant GGPS polypeptide or anyother enzyme introduced in recombinant host cell as disclosed herein,may be not native to a nucleotide sequence coding for the enzyme to beexpressed, i.e. a promoter that is heterologous to the nucleotidesequence (coding sequence) to which it is operably linked. Preferably,the promoter is homologous, i.e. endogenous to the host cell.

Suitable promoters in this context include both constitutive andinducible natural promoters as well as engineered promoters, which arewell known to the person skilled in the art. Suitable promoters in hostcells may be GALT, GAL10, or GAL 1, CYC1, HIS3, ADH1, PGL, PH05, GAPDH,ADC1, TRP1, URA3, LEU2, ENO, TPI, and AOX1. Other suitable promotersinclude PDC, GPD1, PGK1, TEF1, and TDH.

Usually a nucleotide sequence encoding an enzyme comprises a terminator.Any terminator, which is functional in a host cell, may be used in thepresent disclosure. Preferred terminators are obtained from naturalgenes of the host cell. Suitable terminator sequences are well known inthe art. Preferably, such terminators are combined with mutations thatprevent nonsense mediated mRNA decay in the host cell as disclosedherein (see for example: Shirley et al., 2002, Genetics 161:1465-1482).

The disclosure further relates to a vector, preferably an expressionvector, comprising a polynucleotide according to the disclosure or anucleic acid construct according to the disclosure (i.e. comprisingsequence encoding a variant GGPS polypeptide as disclosed herein).

In order to facilitate expression and/or translation of the GGPS, thenucleic acid sequence encoding the GGPS may be comprised in anexpression vector such that the gene encoding the GGPS is operablylinked to the appropriate control sequences for expression and/ortranslation in vitro, or in a host cell as disclosed herein. Theexpression vector may be any vector (e.g., a plasmid or virus), whichcan be conveniently subjected to recombinant DNA procedures and canbring about the expression of the polynucleotide encoding the GGPSvariant polypeptide. The choice of the vector will typically depend onthe compatibility of the vector with the cell into which the vector isto be introduced. The vectors may be linear or closed circular plasmids.The vector may be an autonomously replicating vector, i. e., a vector,which exists as an extra-chromosomal entity, the replication of which isindependent of chromosomal replication, e.g., a plasmid, anextra-chromosomal element, a mini-chromosome, or an artificialchromosome. If intended for use in a host cell of fungal origin, asuitable episomal nucleic acid construct may e.g. be based on the yeast2μ or pKD1 plasmids (Gleer et al., 1991, Biotechnology 9: 968-975), orthe AMA plasmids (Fierro et al., 1995, Curr Genet. 29:482-489).

Alternatively, the expression vector may be one which, when introducedinto the host cell, is integrated into the genome and replicatedtogether with the chromosome(s) into which it has been integrated. Theintegrative cloning vector may integrate at random or at a predeterminedtarget locus in the chromosomes of the host cell. In a preferredembodiment of the disclosure, the integrative cloning vector comprises aDNA fragment, which is homologous to a DNA sequence in a predeterminedtarget locus in the genome of host cell for targeting the integration ofthe cloning vector to this predetermined locus. In order to promotetargeted integration, the cloning vector is preferably linearized priorto transformation of the cell. Linearization is preferably performedsuch that at least one but preferably either end of the cloning vectoris flanked by sequences homologous to the target locus. The length ofthe homologous sequences flanking the target locus is preferably atleast 20 bp, at least 30 bp, at least 50 bp, at least 0.1 kb, at least0.2 kb, at least 0.5 kb, at least 1 kb, at least 2 kb or longer. Theefficiency of targeted integration into the genome of the host cell,i.e. integration in a predetermined target locus, is increased byaugmented homologous recombination abilities of the host cell.

The homologous flanking DNA sequences in the cloning vector, which arehomologous to the target locus, may be derived from a highly expressedlocus meaning that they are derived from a gene, which is capable ofhigh expression level in the host cell. A gene capable of highexpression level, i.e. a highly expressed gene, is herein defined as agene whose mRNA can make up at least 0.5% (w/w) of the total cellularmRNA, e.g. under induced conditions, or alternatively, a gene whose geneproduct can make up at least 1% (w/w) of the total cellular protein, or,in case of a secreted gene product, can be secreted to a level of atleast 0.1 g/I. More typically, the target locus may be an intergeniclocation, so that a gene is not interrupted. Such a locus may alsoprovide for high expression levels. Accordingly, the homologous flankingDNA sequences in the cloning vector may be homologous to an intergenictarget locus

A nucleic acid construct or expression vector may be assembled in vivoin a host cell as disclosed herein and, optionally, integrated into thegenome of the cell in a single step (see, for example, WO2013/076280)

More than one copy of a nucleic acid construct or expression vector asdisclosed herein may be inserted into a host cell to increase productionof the GGPS variant polypeptide (over-expression) encoded by the nucleicacid sequence comprised within the nucleic acid construct. This can bedone, preferably by integrating into its genome two or more copies ofthe nucleic acid, more preferably by targeting the integration of thenucleic acid to a locus defined as defined above.

It will be appreciated by those skilled in the art that the design ofthe expression vector can depend on such factors as the choice of thehost cell to be transformed, the level of expression of protein desired,etc. The expression vectors of the disclosure can be introduced intohost cells to thereby produce proteins or peptides, encoded by nucleicacids as described herein (e.g. a GGPS variant of SEQ ID NO: 1, forexample a functional equivalent or fragment, or a fusion proteincomprising one or more of such variants).

The nucleic acid constructs and vectors disclosed herein can be designedfor expression of the GGPS variant polypeptides in a prokaryotic hostcell or eukaryotic host cell.

A nucleic acid construct and/or expression vector as disclosed hereincan be introduced into prokaryotic or eukaryotic cells via conventionaltransformation or transfection techniques. As used herein, the terms“transformation” and “transfection” are intended to refer to a varietyof art-recognized techniques for introducing foreign nucleic acid (e.g.,DNA) into a host cell well known to those skilled in the art. Suitablemethods for transforming or transfecting host cells can be found inSambrook, et al. (Molecular Cloning: A Laboratory Manual, 2nd,ed. ColdSpring Harbor Laboratory, Cold Spring Harbor Laboratory Press, ColdSpring Harbor, N.Y., 1989), Davis et al., Basic Methods in MolecularBiology (1986) and other laboratory manuals.

The terms “functional equivalents” and “functional variants” are usedinterchangeably herein. Functional equivalents according to thedisclosure are isolated nucleic acid fragments that encode a polypeptidethat exhibits a particular function of a GGPS variant as defined herein.Functional equivalents therefore also encompass biologically activefragments and are themselves encompassed within the term “a GGPSvariant” of the disclosure.

Preferably, a functional equivalent of the disclosure comprises one ormore of the substitutions described herein. However, a functionalequivalent may comprise one or more modifications in addition to thesubstitutions described above.

Functional nucleic acid equivalents may typically contain silentmutations or mutations that do not alter the biological function of theencoded GGPS variant polypeptide. Accordingly, the disclosure providesnucleic acid molecules encoding a variant GGPS protein that containschanges in amino acid residues that are not essential for a particularbiological activity, i.e. GGPS activity.

Such functional equivalents of GGPS variant proteins differ in aminoacid sequence from the parent GGPS variant sequence from which they arederived yet retain at least one biological activity thereof, preferablythey retain at least GGPS activity. The skilled person will recognisethat changes can be introduced by mutation into the nucleotide sequencesaccording to the disclosure thereby leading to changes in the amino acidsequence of the resulting protein without substantially altering thefunction of such a protein.

In one embodiment the isolated nucleic acid molecule comprises anucleotide sequence encoding a protein, wherein the protein comprises anamino acid sequence having at least about 60%, 65%, 70%, 75%, 80%, 85%,90%, 95%, 96%, 97%, 98%, 99% identity with the parent GGPS variant or tothe reference amino acid sequence (for example that shown in SEQ ID NO:1 or SEQ ID NO: 17).

Accordingly, a functional equivalent of a GGPS variant according to thedisclosure is preferably a protein which comprises an amino acidsequence having at least about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%,96%, 97%, 98%, 99% or more identity to the parent GGPS variant aminoacid sequence or reference polypeptide sequence, for example that shownin SEQ ID NO: 1 or SEQ ID NO: 17, and typically also retains at leastone functional activity of the parent GGPS polypeptide.

A variant polypeptide of the disclosure having GGPS activity maycomprise an amino acid sequence having at least about 80% sequenceidentity, at least about 90% sequence identity, at least about 95%sequence identity, at least about 96%, at least about 97%, at leastabout 98% or at least about 99% sequence identity to any one of SEQ IDNO: 3, SEQ ID NO: 5, SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 11, SEQ IDNO: 13 or SEQ ID NO: 15 or SEQ ID NO: 18 to 33.

A variant polypeptide of the disclosure may have a sequence as definedin Table 2 or a substitution pattern as defined in Table 2 (in terms ofposition(s), if not precisely the same amino acid substitution).

Variant GGPS polypeptides as disclosed herein may be identified e.g. byscreening libraries of mutants, e.g. substitution mutants, of a suitablereference polypeptide. Candidate mutants may be screened on the basis oftheir ability to increase steviol or steviol glycoside production, whenexpressed in a host cell (in comparison with a corresponding host cellexpressing the reference polypeptide).

Fragments of a nucleic acid as disclosed herein may comprise or consistor sequences not encoding functional polypeptides. Such nucleic acidsmay function as probes or primers for a PCR reaction.

Nucleic acids according to the disclosure irrespective of whether theyencode functional or non-functional polypeptides can be used ashybridization probes or polymerase chain reaction (PCR) primers. Uses ofthe nucleic acid molecules of the present disclosure that do not encodea polypeptide having GGPS activity include, inter alia, (1) in situhybridization (e.g. FISH) to metaphase chromosomal spreads to provideprecise chromosomal location of an GGPS-encoding gene as described inVerma et al., Human Chromosomes: a Manual of Basic Techniques, PergamonPress, New York (1988); (2) Northern blot analysis for detectingexpression of GGPS mRNA in specific tissues and/or cells; and (3) probesand primers that can be used as a diagnostic tool to analyse thepresence of a nucleic acid hybridizable to such a probe or primer in agiven biological (e.g. tissue) sample.

Variants of a given reference GGPS enzyme can be obtained by thefollowing standard procedure:

-   -   Mutagenesis (error-prone, doped oligo, spiked oligo) or        synthesis of variants    -   Transformation in, for example, Y. lipolitica or S. cerevisiae    -   Cultivation of transformants, selection of transformants    -   Expression in, for example, Y. lipolitica or S. cerevisiae    -   Primary Screening, for example on the basis of steviol or        steviol glycoside production    -   Identification of an improved variant (for example in relation        to altered co-factor specificity)

In one embodiment the disclosure relates to a method of producing a GGPSpolypeptide variant according to the disclosure, which method comprises:

a) selecting a reference GGPS polypeptide (i.e. a template or startingpolypeptide);

b) substituting at least one amino acid residue corresponding to any of

92, 100 or 235

said positions being defined with reference to SEQ ID NO: 1;

c) optionally substituting one or more further amino acids as defined inb);

d) preparing the variant resulting from steps a)-c);

e) determining a property of the variant, for example as set out in theExamples; and

f) selecting a variant with an altered property in comparison to thereference GGPS polypeptide.

In a preferred embodiment in the method of producing a GGPS polypeptidevariant as disclosed herein, the reference GGPS polypeptide has thesequence set out in SEQ ID NO: 1.

More preferably in step b) of the method according to the disclosure atleast one amino acid residue corresponding to any of

92, 100 or 235

is substituted, said positions being defined with reference to SEQ IDNO: 1. The reference polypeptide may have at least about 80% homologywith SEQ ID NO: 1.

In another embodiment, the disclosure features host cells, e.g.,transformed host cells or recombinant host cells that contain a nucleicacid, nucleic acid construct or vector of the disclosure. A “host cell”or “recombinant cell” according to the disclosure is typically a cellinto which (or into an ancestor of which) has been introduced, by meansof recombinant DNA techniques, a nucleic acid according to thedisclosure, i.e. a nucleic acid encoding a GGPS of the disclosure. Inthe context of the present disclosure a “host cell” according to thedisclosure or a parent of said host cell may be any type of host cell.

Thus, a host cell as disclosed herein may comprise a recombinant nucleicacid encoding one or more variant polypeptides of the disclosure.

A host cell may be a eukaryotic or a prokaryotic cell. Accordingly, bothprokaryotic and eukaryotic cells are included, e.g., bacteria, fungi,yeast, and the like, especially preferred are cells from yeasts, forexample, S. cerevisiae, Y. lipolytica and K. lactis. Host cells alsoinclude, but are not limited to, mammalian cell lines such as CHO, VERO,BHK, HeLa, COS, MDCK, 293, 3T3, WI38, and choroid plexus cell lines.

The disclosure thus provides a method for producing a GGPS, which methodcomprises cultivating a host cell as described herein under conditionssuitable for production of the GGPS and, optionally, recovering theGGPS. Typically the host cell is capable of producing steviol or asteviol glycoside.

A recombinant host according to the disclosure may comprise anypolypeptide as described herein. Typically, a recombinant host accordingto the disclosure is capable of producing a steviol glycoside.Typically, said recombinant host is capable of producing a glycosylatedditerpene, such as a steviol glycoside. For example, a recombinant hostaccording to the disclosure may be capable of producing one or more of,for example, steviol-13-monoside, steviol-19-monoside,13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester, rubusoside, stevioside,steviol-19-diside, steviolbioside, rebaudiosideA, rebaudiosideE,rebaudiosideD or rebaudiosideM.

A recombinant host according to the disclosure may comprise one or morerecombinant nucleic acid sequences encoding one or more polypeptideshaving UDP-glycosyltransferase (UGT) activity.

For the purposes of this disclosure, a polypeptide having UGT activityis one which has glycosyltransferase activity (EC 2.4), i.e. that canact as a catalyst for the transfer of a monosaccharide unit from anactivated nucleotide sugar (also known as the “glycosyl donor”) to aglycosyl acceptor molecule, usually an alcohol. The glycosyl donor for aUGT is typically the nucleotide sugar uridine diphosphate glucose(uracil-diphosphate glucose, UDP-glucose).

Such additional UGTs may be selected so as to produce a desired steviolglycoside. Schematic diagrams of steviol glycoside formation are set outin Humphrey et al., Plant Molecular Biology (2006) 61: 47-62 and Mohamedet al., J. Plant Physiology 168 (2011) 1136-1141. In addition, FIG. 1sets out a schematic diagram of steviol glycoside formation.

A recombinant host according to the disclosure may thus comprise one ormore recombinant nucleic acid sequences encoding one or more of:

(i) a polypeptide having UGT74G1 activity;

(ii) a polypeptide having UGT2 activity;

(ii) a polypeptide having UGT85C2 activity; and

(iii) a polypeptide having UGT76G1 activity.

A recombinant yeast suitable for use in the present disclosure maycomprise a nucleotide sequence encoding a polypeptide capable ofcatalyzing the addition of a C-13-glucose to steviol. That is to say, arecombinant yeast suitable for use in a method of the disclosure maycomprise a UGT which is capable of catalyzing a reaction in whichsteviol is converted to steviolmonoside.

Such a recombinant yeast suitable for use in a method of the disclosuremay comprise a nucleotide sequence encoding a polypeptide having theactivity shown by UDP-glycosyltransferase (UGT) UGT85C2, whereby thenucleotide sequence upon transformation of the yeast confers on thatyeast the ability to convert steviol to steviolmonoside.

UGT85C2 activity is transfer of a glucose unit to the 13-OH of steviol.

Thus, a suitable UGT85C2 may function as a uridine 5′-diphosphoglucosyl: steviol 13-OH transferase, and a uridine 5′-diphosphoglucosyl: steviol- 19-0-glucoside 13-OH transferase. A functionalUGT85C2 polypeptides may also catalyze glucosyl transferase reactionsthat utilize steviol glycoside substrates other than steviol andsteviol- 19-O-glucoside. Such sequences may be referred to as UGT1sequences herein.

A recombinant yeast suitable for use in the present disclosure maycomprise a nucleotide sequence encoding a polypeptide which has UGT2activity.

A polypeptide having UGT2 activity is one which functions as a uridine5′-diphospho glucosyl: steviol- 13-O-glucoside transferase (alsoreferred to as a steviol-13-monoglucoside 1,2-glucosylase), transferringa glucose moiety to the C-2′ of the 13-O-glucose of the acceptormolecule, steviol-13-O-glucoside. Typically, a suitable UGT2 polypeptidealso functions as a uridine 5′-diphospho glucosyl: rubusosidetransferase transferring a glucose moiety to the C-2′ of the13-O-glucose of the acceptor molecule, rubusoside.

A polypeptide having UGT2 activity may also catalyze reactions thatutilize steviol glycoside substrates other than steviol-13-0-glucosideand rubusoside, e.g., functional UGT2 polypeptides may utilizestevioside as a substrate, transferring a glucose moiety to the C-2′ ofthe 19-O-glucose residue to produce rebaudioside E. A functional UGT2polypeptides may also utilize rebaudioside A as a substrate,transferring a glucose moiety to the C-2′ of the 19-O-glucose residue toproduce rebaudioside D. However, a functional UGT2 polypeptide typicallydoes not transfer a glucose moiety to steviol compounds having a1,3-bound glucose at the C-13 position, i.e., transfer of a glucosemoiety to steviol 1,3-bioside and 1,3-stevioside typically does notoccur.

A polypeptide having UGT2 activity may also transfer sugar moieties fromdonors other than uridine diphosphate glucose. For example, apolypeptide having UGT2 activity act as a uridine 5′-diphosphoD-xylosyl: steviol-13-O-glucoside transferase, transferring a xylosemoiety to the C-2′ of the 13-O-glucose of the acceptor molecule,steviol-13-O-glucoside. As another example, a polypeptide having UGT2activity may act as a uridine 5′-diphospho L-rhamnosyl:steviol-13-0-glucoside transferase, transferring a rhamnose moiety tothe C-2′ of the 13-O-glucose of the acceptor molecule, steviol.

A recombinant yeast suitable for use in the method according to thedisclosure may comprise a nucleotide sequence encoding a polypeptidehaving UGT activity capable of catalyzing the addition of a C-19-glucoseto steviolbioside. That is to say, a recombinant yeast of the disclosuremay comprise a UGT which is capable of catalyzing a reaction in whichsteviolbioside is converted to stevioside. Accordingly, such arecombinant yeast may be capable of converting steviolbioside tostevioside. Expression of such a nucleotide sequence may confer on therecombinant yeast the ability to produce at least stevioside.

A recombinant yeast suitable for use in a method according to thedisclosure may thus also comprise a nucleotide sequence encoding apolypeptide having the activity shown by UDP-glycosyltransferase (UGT)UGT74G1, whereby the nucleotide sequence upon transformation of theyeast confers on the cell the ability to convert steviolbioside tostevioside.

Suitable UGT74G1 polypeptides may be capable of transferring a glucoseunit to the 13-OH or the 19-COOH of steviol. A suitable UGT74G1polypeptide may function as a uridine 5′-diphospho glucosyl: steviol19-COOH transferase and a uridine 5′-diphospho glucosyl: steviol-13-O-glucoside 19-COOH transferase. Functional UGT74G1 polypeptides alsomay catalyze glycosyl transferase reactions that utilize steviolglycoside substrates other than steviol and steviol-13-O-glucoside, orthat transfer sugar moieties from donors other than uridine diphosphateglucose. Such sequences may be referred to herein as UGT3 sequences.

A recombinant yeast suitable for use in a method according to thedisclosure may comprise a nucleotide sequence encoding a polypeptidecapable of catalyzing glucosylation of the C-3′ of the glucose at theC-13 position of stevioside. That is to say, a recombinant yeastsuitable for use in a method according to the disclosure may comprise aUGT which is capable of catalyzing a reaction in which stevioside isconverted to rebaudioside A. Accordingly, such a recombinant yeast maybe capable of converting stevioside to rebaudioside A. Expression ofsuch a nucleotide sequence may confer on the yeast the ability toproduce at least rebaudioside A.

A recombinant yeast suitable for use in a method of the invention maythus also comprise a nucleotide sequence encoding a polypeptide havingthe activity shown by UDP-glycosyltransferase (UGT) UGT76G1, whereby thenucleotide sequence upon transformation of a yeast confers on that yeastthe ability to convert stevioside to rebaudioside A.

A suitable UGT76G1 adds a glucose moiety to the C-3′of theC-13-O-glucose of the acceptor molecule, a steviol 1,2 glycoside. Thus,UGT76G1 functions, for example, as a uridine 5′-diphospho glucosyl:steviol 13-0-1,2 glucoside C-3′ glucosyl transferase and a uridine5′-diphospho glucosyl: steviol- 19-0-glucose, 13-0-1,2 bioside C-3′glucosyl transferase. Functional UGT76G1 polypeptides may also catalyzeglucosyl transferase reactions that utilize steviol glycoside substratesthat contain sugars other than glucose, e.g., steviol rhamnosides andsteviol xylosides. Such sequences may be referred to herein as UGT4sequences. A UGT4 may alternatively or in addition be capable ofconverting RebD to RebM.

A recombinant yeast suitable for use in a method of the disclosuretypically comprises nucleotide sequences encoding at least onepolypeptide having UGT1 activity, at least one polypeptide having UGT2activity, at least one polypeptide having UGT3 activity and at least onepolypeptide having UGT4 activity. One or more of these nucleic acidsequences may be recombinant. A given nucleic acid may encode apolypeptide having one or more of the above activities. For example, anucleic acid may encode a polypeptide which has two, three or four ofthe activities set out above. Preferably, a recombinant yeast for use inthe method of the disclosure comprises UGT1, UGT2 and UGT3 and UGT4activity. Suitable UGT1, UGT2, UGT3 and UGT4 sequences are described inTable 1 of WO2015/007748.

A recombinant host of the disclosure may comprise two or more nucleicacid sequences encoding a polypeptide having any one UGT activity, forexample UGT1, 2, 3 or 4, activity. Where a recombinant host of thedisclosure comprises two or more nucleic acid sequence encoding apolypeptide having any one UGT activity, those nucleic acid sequencesmay be the same or different and/or may encode the same or differentpolypeptides. In particular, a recombinant host of the disclosure maycomprise a nucleic acid sequence encoding a two different UGT2polypeptides.

A recombinant host according to the disclosure may comprise one or morerecombinant nucleotide sequence(s) encoding one of more of:

-   -   a polypeptide having ent-copalyl pyrophosphate synthase        activity;    -   a polypeptide having ent-Kaurene synthase activity;    -   a polypeptide having ent-Kaurene oxidase activity; and    -   a polypeptide having kaurenoic acid 13-hydroxylase activity.

For the purposes of this disclosure, a polypeptide having ent-copalylpyrophosphate synthase (EC 5.5.1.13) is capable of catalyzing thechemical reaction:

This enzyme has one substrate, geranylgeranyl pyrophosphate, and oneproduct, ent-copalyl pyrophosphate. This enzyme participates ingibberellin biosynthesis. This enzyme belongs to the family ofisomerase, specifically the class of intramolecular lyases. Thesystematic name of this enzyme class is ent-copalyl-diphosphate lyase(decyclizing). Other names in common use include having ent-copalylpyrophosphate synthase, ent-kaurene synthase A, and ent-kaurenesynthetase A.

Suitable nucleic acid sequences encoding an ent-copalyl pyrophosphatesynthase may for instance comprise a sequence as set out in SEQ ID. NO:1, 3, 5, 7, 17, 19, 59, 61, 141, 142, 151, 152, 153, 154, 159, 160, 182or 184 of WO2015/007748.

For the purposes of this disclosure, a polypeptide having ent-kaurenesynthase activity (EC 4.2.3.19) is a polypeptide that is capable ofcatalyzing the chemical reaction:

ent-copalyl diphosphate

ent-kaurene+diphosphate

Hence, this enzyme has one substrate, ent-copalyl diphosphate, and twoproducts, ent-kaurene and diphosphate.

This enzyme belongs to the family of lyases, specifically thosecarbon-oxygen lyases acting on phosphates. The systematic name of thisenzyme class is ent-copalyl-diphosphate diphosphate-lyase (cyclizing,ent-kaurene-forming). Other names in common use include ent-kaurenesynthase B, ent-kaurene synthetase B, ent-copalyl-diphosphatediphosphate-lyase, and (cyclizing). This enzyme participates inditerpenoid biosynthesis.

Suitable nucleic acid sequences encoding an ent-Kaurene synthase may forinstance comprise a sequence as set out in SEQ ID. NO: 9, 11, 13, 15,17, 19, 63, 65, 143, 144, 155, 156, 157, 158, 159, 160, 183 or 184 ofWO2015/007748.

ent-copalyl diphosphate synthases may also have a distinct ent-kaurenesynthase activity associated with the same protein molecule. Thereaction catalyzed by ent-kaurene synthase is the next step in thebiosynthetic pathway to gibberellins. The two types of enzymic activityare distinct, and site-directed mutagenesis to suppress the ent-kaurenesynthase activity of the protein leads to build up of ent-copalylpyrophosphate.

Accordingly, a single nucleotide sequence used in a recombinant hostcell of the disclosure may encode a polypeptide having ent-copalylpyrophosphate synthase activity and ent-kaurene synthase activity.Alternatively, the two activities may be encoded two distinct, separatenucleotide sequences.

For the purposes of this disclosure, a polypeptide having ent-kaureneoxidase activity (EC 1.14.13.78) is a polypeptide which is capable ofcatalysing three successive oxidations of the 4-methyl group ofent-kaurene to give kaurenoic acid. Such activity typically requires thepresence of a cytochrome P450.

Suitable nucleic acid sequences encoding an ent-Kaurene oxidase may forinstance comprise a sequence as set out in SEQ ID. NO: 21, 23, 25, 67,85, 145, 161, 162, 163, 180 or 186 of WO2015/007748.

For the purposes of the disclosure, a polypeptide having kaurenoic acid13-hydroxylase activity (EC 1.14.13) is one which is capable ofcatalyzing the formation of steviol (ent-kaur-16-en-13-ol-19-oic acid)using NADPH and O₂. Such activity may also be referred to as ent-ka13-hydroxylase activity.

Suitable nucleic acid sequences encoding a kaurenoic acid 13-hydroxylasemay for instance comprise a sequence as set out in SEQ ID. NO: 27, 29,31, 33, 69, 89, 91, 93, 95, 97, 146, 164, 165, 166, 167 or 185 ofWO2015/007748.

A recombinant host of the disclosure may comprise a recombinant nucleicacid sequence encoding a polypeptide having NADPH-cytochrome p450reductase activity. That is to say, a recombinant host of the disclosuremay be capable of expressing a nucleotide sequence encoding apolypeptide having NADPH-cytochrome p450 reductase activity. For thepurposes of the disclosure, a polypeptide having NADPH-Cytochrome P450reductase activity (EC 1.6.2.4; also known as NADPH:ferrihemoproteinoxidoreductase, NADPH:hemoprotein oxidoreductase, NADPH:P450oxidoreductase, P450 reductase, POR, CPR, CYPOR) is typically one whichis a membrane-bound enzyme allowing electron transfer to cytochrome P450in the microsome of the eukaryotic cell from a FAD- and FMN-containingenzyme NADPH:cytochrome P450 reductase (POR; EC 1.6.2.4).

In a recombinant host cell of the disclosure, the ability of the hostcell to produce geranylgeranyl diphosphate (GGPP) may be upregulated(other than by use of a nucleotide sequence(s) encoding one or morepolypeptide of the disclosure). Upregulated in the context of thisdisclosure implies that the recombinant host cell produces more GGPPthan an equivalent non-recombinant host cell.

Accordingly, a recombinant host of the disclosure may comprise one ormore nucleotide sequence(s) encoding hydroxymethylglutaryl-CoAreductase, farnesyl-pyrophosphate synthetase and geranylgeranyldiphosphate synthase, whereby the nucleotide sequence(s) upontransformation of the microorganism confer(s) on the microorganism theability to produce elevated levels of GGPP. Thus, a recombinant hostaccording to the disclosure may comprise one or more recombinant nucleicacid sequence(s) encoding one or more of hydroxymethylglutaryl-CoAreductase, farnesyl-pyrophosphate synthetase and geranylgeranyldiphosphate synthase (different from a GGPS of the disclosure).

Accordingly, a recombinant host of the disclosure may comprise nucleicacid sequences encoding one or more of:

a polypeptide having hydroxymethylglutaryl-CoA reductase activity;

a polypeptide having farnesyl-pyrophosphate synthetase activity;

a polypeptide having geranylgeranyl diphosphate synthase activity.

A host or host cell as defined herein is an organism suitable forgenetic manipulation and one which may be cultured at cell densitiesuseful for industrial production of a target product. A suitable hostmay be a microorganism, for example one which may be maintained in afermentation device. A host cell may be a host cell found in nature or ahost cell derived from a parent host cell after genetic manipulation orclassical mutagenesis.

As used herein, a recombinant host is one which is genetically modifiedor transformed/transfected with one or more of nucleotide sequenceencoding a variant GGS as defined herein. The presence of the one ormore such nucleotide sequences alters the ability of the microorganismto produce steviol or a steviol glycoside, in particular one or moresteviol glycosides. A non-recombinant host, i.e. one that is nottransformed/transfected or genetically modified, typically does notcomprise one or more of the nucleotide sequences enabling the cell toproduce a steviol glycoside. Hence, a non-recombinant host is typicallya host that does not naturally produce a steviol glycoside, although ahost which naturally produces a steviol or a steviol glycoside and whichhas been modified according to the disclosure (and which thus has analtered ability to produce a diterpene glycoside) is considered arecombinant host according to the disclosure.

In particular, it may be possible that the enzymes selected from thegroup consisting of ent-copalyl pyrophosphate synthase, ent-Kaurenesynthase, ent-Kaurene oxidase, and kaurenoic acid 13-hydroxylase, UGTs,hydroxymethylglutaryl-CoA reductase, farnesyl-pyrophosphate synthetase,geranylgeranyl diphosphate synthase (different from a GGPS of thedisclosure) and NADPH-cytochrome p450 reductase are native to the hostand that transformation with one or more of the nucleotide sequencesencoding these enzymes may not be required to confer the host cell theability to produce steviol or a steviol glycoside. A host according tothe present disclosure may be a recombinant host which is naturallycapable of producing GGPP (i.e. in its non-recombinant form).

Further improvement of steviol or steviol glycoside production by thehost microorganism may be obtained by classical strain improvement.

A host cell may be a prokaryotic, archaebacterial or eukaryotic hostcell.

A prokaryotic host cell may be, but is not limited to, a bacterial hostcell. An eukaryotic host cell may be, but is not limited to, a yeast, afungus, an amoeba, an algae, an animal, an insect host cell.

An eukaryotic host cell may be a fungal host cell. “Fungi” include allspecies of the subdivision Eumycotina (Alexopoulos, C. J., 1962, In:Introductory Mycology, John Wiley & Sons, Inc., New York). The termfungus thus includes among others filamentous fungi and yeast.

“Filamentous fungi” are herein defined as eukaryotic microorganisms thatinclude all filamentous forms of the subdivision Eumycotina and Oomycota(as defined by Hawksworth et al., 1995, supra). The filamentous fungiare characterized by a mycelial wall composed of chitin, cellulose,glucan, chitosan, mannan, and other complex polysaccharides. Vegetativegrowth is by hyphal elongation and carbon catabolism is obligatoryaerobic. Filamentous fungal strains include, but are not limited to,strains of Acremonium, Aspergillus, Agaricus, Aureobasidium,Cryptococcus, Corynascus, Chrysosporium, Filibasidium, Fusarium,Humicola, Magnaporthe, Monascus, Mucor, Myceliophthora, Mortierella,Neocallimastix, Neurospora, Paecilomyces, Penicillium, Piromyces,Phanerochaete Podospora, Pycnoporus, Rhizopus, Schizophyllum, Sordaria,Talaromyces, Rasmsonia, Thermoascus, Thielavia, Tolypocladium, Trametesand Trichoderma. Preferred filamentous fungal strains that may serve ashost cells belong to the species Aspergillus niger, Aspergillus oryzae,Aspergillus fumigatus, Penicillium chrysogenum, Penicillium citrinum,Acremonium chrysogenum, Trichoderma reesei, Rasamsonia emersonii(formerly known as Talaromyces emersonii), Aspergillus sojae,Chrysosporium lucknowense, Myceliophtora thermophyla. Reference hostcells for the comparison of fermentation characteristics of transformedand untransformed cells, include e.g. Aspergillus niger CBS120.49, CBS513.88, Aspergillus oryzae ATCC16868, ATCC 20423, IFO 4177, ATCC 1011,ATCC 9576, ATCC14488-14491, ATCC 11601, ATCC12892, Aspergillus fumigatusAF293 (CBS101355), P. chrysogenum CBS 455.95, Penicillium citrinum ATCC38065, Penicillium chrysogenum P2, Acremonium chrysogenum ATCC 36225,ATCC 48272, Trichoderma reesei ATCC 26921, ATCC 56765, ATCC 26921,Aspergillus sojae ATCC11906, Chrysosporium lucknowense ATCC44006 andderivatives of all of these strains. Particularly preferred asfilamentous fungal host cell are Aspergillus niger CBS 513.88 andderivatives thereof.

An eukaryotic host cell may be a yeast cell. Preferred yeast host cellsmay be selected from the genera: Saccharomyces (e.g., S. cerevisiae, S.bayanus, S. pastorianus, S. carlsbergensis), Brettanomyces,Kluyveromyces, Candida (e.g., C. krusei, C. revkaufi, C. pulcherrima, C.tropicalis, C. utilis), Issatchenkia (eg. I. orientalis) Pichia (e.g.,P. pastoris), Schizosaccharomyces, Hansenula, Kloeckera, Pachysolen,Schwanniomyces, Trichosporon, Yarrowia (e.g., Y. lipolytica (formerlyclassified as Candida lipolytica)), Yamadazyma.

Prokaryotic host cells may be bacterial host cells. Bacterial host cellmay be Gram negative or Gram-positive bacteria. Examples of bacteriainclude, but are not limited to, bacteria belonging to the genusBacillus (e.g., B. subtilis, B. amyloliquefaciens, B. licheniformis, B.puntis, B. megaterium, B. halodurans, B. pumilus,), Acinetobacter,Nocardia, Xanthobacter, Escherichia (e.g., E. coli (e.g., strains DH 1OB, Stbl2, DH5-alpha, DB3, DB3.1), DB4, DBS, JDP682 and ccdA-over (e.g.,U.S. application Ser. No. 09/518,188))), Streptomyces, Erwinia,Klebsiella, Serratia (e.g., S. marcessans), Pseudomonas (e.g., P.aeruginosa), Salmonella (e.g., S. typhimurium, S. typhi). Bacteria alsoinclude, but are not limited to, photosynthetic bacteria (e.g., greennon-sulfur bacteria (e.g., Choroflexus bacteria (e.g., C. aurantiacus),Chloronema (e.g., C. gigateum)), green sulfur bacteria (e.g., Chlorobiumbacteria (e.g., C. limicola), Pelodictyon (e.g., P. luteolum), purplesulfur bacteria (e.g., Chromatium (e.g., C. okenii)), and purplenon-sulfur bacteria (e.g., Rhodospirillum (e.g., R. rubrum), Rhodobacter(e.g. R. sphaeroides, R. capsulatus), and Rhodomicrobium bacteria (e.g.,R. vanellii)).

Host Cells may be host cells from non-microbial organisms. Examples ofsuch cells, include, but are not limited to, insect cells (e.g.,Drosophila (e.g., D. melanogaster), Spodoptera (e.g., S. frugiperda Sf9or Sf21 cells) and Trichoplusa (e.g., High-Five cells); nematode cells(e.g., C. elegans cells); avian cells; amphibian cells (e.g., Xenopuslaevis cells); reptilian cells; and mammalian cells (e.g., NIH3T3, 293,CHO, COS, VERO, C127, BHK, Per-C6, Bowes melanoma and HeLa cells).

The disclosure further provides a method for producing a polypeptide ofthe disclosure comprising:

-   -   (a) cultivating a recombinant host cell of the disclosure under        conditions conducive to the production of the polypeptide by the        host cell, and optionally,    -   (b) recovering the polypeptide.

A recombinant host according to the present disclosure may be able togrow on any suitable carbon source known in the art and convert it to asteviol glycoside, e.g. a steviol glycoside. The recombinant host may beable to convert directly plant biomass, celluloses, hemicelluloses,pectines, rhamnose, galactose, fucose, maltose, maltodextrines, ribose,ribulose, or starch, starch derivatives, sucrose, glucose, lactose orglycerol. Hence, a preferred host expresses enzymes such as cellulases(endocellulases and exocellulases) and hemicellulases (e.g. endo- andexo-xylanases, arabinases) necessary for the conversion of celluloseinto glucose monomers and hemicellulose into xylose and arabinosemonomers, pectinases able to convert pectines into glucuronic acid andgalacturonic acid or amylases to convert starch into glucose monomers.Preferably, the host is able to convert a carbon source selected fromthe group consisting of glucose, xylose, arabinose, sucrose, lactose andglycerol. The host cell may for instance be a eukaryotic host cell asdescribed in WO03/062430, WO06/009434, EP1499708B1, WO2006096130 orWO04/099381.

Thus, in a further aspect, the disclosure also provides a process forthe preparation of a steviol glycoside which comprises fermenting arecombinant host of the disclosure which is capable of producing atleast one steviol glycoside in a suitable fermentation medium, andoptionally recovering the steviol glycoside.

The steviol glycoside may be, for example, steviol-13-monoside,steviol-19-monoside, 13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester, rubusoside, stevioside,steviol-19-diside, steviolbioside, rebA, rebaudioside B, rebaudioside C,rebaudioside E, rebaudioside D or rebaudioside M.

The fermentation medium used in the process for the production of asteviol glycoside may be any suitable fermentation medium which allowsgrowth of a particular host cell. The essential elements of thefermentation medium are known to the person skilled in the art and maybe adapted to the host cell selected.

Preferably, the fermentation medium comprises a carbon source selectedfrom the group consisting of plant biomass, celluloses, hemicelluloses,pectines, rhamnose, galactose, fucose, fructose, maltose,maltodextrines, ribose, ribulose, or starch, starch derivatives,glucose, sucrose, lactose, fatty acids, triglycerides and glycerol.Preferably, the fermentation medium also comprises a nitrogen sourcesuch as ureum, or an ammonium salt such as ammonium sulphate, ammoniumchloride, ammoniumnitrate or ammonium phosphate.

The fermentation process according to the present disclosure may becarried out in batch, fed-batch or continuous mode. A separatehydrolysis and fermentation (SHF) process or a simultaneoussaccharification and fermentation (SSF) process may also be applied. Acombination of these fermentation process modes may also be possible foroptimal productivity. A SSF process may be particularly attractive ifstarch, cellulose, hemicelluose or pectin is used as a carbon source inthe fermentation process, where it may be necessary to add hydrolyticenzymes, such as cellulases, hemicellulases or pectinases to hydrolysethe substrate.

The recombinant host used in the process for the preparation of asteviol glycoside may be any suitable recombinant host as defined hereinabove. It may be advantageous to use a recombinant eukaryotic hostaccording to the disclosure in the process since most eukaryotic cellsdo not require sterile conditions for propagation and are insensitive tobacteriophage infections. In addition, eukaryotic host cells may begrown at low pH to prevent bacterial contamination.

The recombinant host according to the present disclosure may be afacultative anaerobic microorganism. A facultative anaerobic recombinanthost can be propagated aerobically to a high cell concentration. Thisanaerobic phase can then be carried out at high cell density whichreduces the fermentation volume required substantially, and may minimizethe risk of contamination with aerobic microorganisms.

The fermentation process for the production of a steviol glycosideaccording to the present disclosure may be an aerobic or an anaerobicfermentation process.

An anaerobic fermentation process may be herein defined as afermentation process run in the absence of oxygen or in whichsubstantially no oxygen is consumed, preferably less than 5, 2.5 or 1mmol/L/h, and wherein organic molecules serve as both electron donor andelectron acceptors. The fermentation process according to the presentdisclosure may also first be run under aerobic conditions andsubsequently under anaerobic conditions.

The fermentation process may also be run under oxygen-limited, ormicro-aerobical, conditions. Alternatively, the fermentation process mayfirst be run under aerobic conditions and subsequently underoxygen-limited conditions. An oxygen-limited fermentation process is aprocess in which the oxygen consumption is limited by the oxygentransfer from the gas to the liquid. The degree of oxygen limitation isdetermined by the amount and composition of the ingoing gasflow as wellas the actual mixing/mass transfer properties of the fermentationequipment used.

The production of a steviol glycoside in the process according to thepresent disclosure may occur during the growth phase of the host cell,during the stationary (steady state) phase or during both phases. It maybe possible to run the fermentation process at different temperatures.

The process for the production of a steviol glycoside may be run at atemperature which is optimal for the recombinant host. The optimumgrowth temperature may differ for each transformed recombinant host andis known to the person skilled in the art. The optimum temperature mightbe higher than optimal for wild type organisms to grow the organismefficiently under non-sterile conditions under minimal infectionsensitivity and lowest cooling cost. Alternatively, the process may becarried out at a temperature which is not optimal for growth of therecombinant host.

The process for the production of a steviol glycoside according to thepresent disclosure may be carried out at any suitable pH value. If therecombinant host is a yeast, the pH in the fermentation mediumpreferably has a value of below 6, preferably below 5,5, preferablybelow 5, preferably below 4,5, preferably below 4, preferably below pH3,5 or below pH 3,0, or below pH 2,5, preferably above pH 2. Anadvantage of carrying out the fermentation at these low pH values isthat growth of contaminant bacteria in the fermentation medium may beprevented.

Such a process may be carried out on an industrial scale. The product ofsuch a process is one or more steviol glycosides, such one or more of,for example, steviol-13-monoside, steviol-19-monoside,13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester, rubusoside, stevioside,steviol-19-diside, steviolbioside, rebaudiosideA, rebaudiosideE,rebaudiosideD or rebaudiosideM.

Recovery of steviol glycoside(s) from the fermentation medium may beperformed by known methods in the art, for instance by distillation,vacuum extraction, solvent extraction, or evaporation.

In the process for the production of a steviol glycoside according tothe disclosure, it may be possible to achieve a concentration of above 5mg/l fermentation broth, preferably above 10 mg/l, preferably above 20mg/l, preferably above 30 mg/l fermentation broth, preferably above 40mg/l, more preferably above 50 mg/l, preferably above 60 mg/l,preferably above 70, preferably above 80 mg/l, preferably above 100mg/l, preferably above 1 g/l, preferably above 5 g/l, preferably above10 g/l, but usually below 70 g/l.

The disclosure further provides a fermentation broth comprising asteviol glycoside obtainable by the process of the disclosure for thepreparation of a steviol glycoside.

In the event that one or more steviol glycosides is expressed within themicroorganism, such cells may need to be treated so as to release them.Preferentially, at least one steviol glycoside, for example rebA, reb Dor rebM, is produced extracellularly.

A broth according to the disclosure may comprise more than at least onesteviol glycoside, such as rebA, rebD or rebM, as compared with a brothproduced from a recombinant host in which a reference polypeptide isexpressed instead of a polypeptide of the disclosure.

A broth may be defined as the total broth, i.e. including a host cell ofthe disclosure or may be defined in terms of the liquid phase onceseparated away from a host cell of the disclosure, for example thesupernatant.

A broth according to the disclosure may comprise less of at least onenon-steviol glycoside, for example one or more kaurenoic acidglycosides, as compared with a broth produced from a recombinant host inwhich a reference polypeptide is expressed instead of a polypeptide ofthe disclosure.

The disclosure also provides a steviol glycoside obtained by a processaccording to the disclosure for the preparation of a steviol glycosideor obtainable from a fermentation broth of the disclosure. Such asteviol glycoside may be a non- naturally occurring steviol glycoside,that is to say one which is not produced in plants.

Also provided is a composition comprising two or more steviol glycosidesobtainable by a process of the disclosure for the preparation of asteviol glycoside or obtainable from a fermentation broth of thedisclosure. In such a composition, one or more of the steviol glycosidesmay be a non- naturally occurring steviol glycoside, that is to say onewhich is not produced in plants.

Furthermore, the disclosure provides a method for converting a firststeviol glycoside into a second steviol glycoside, which methodcomprises:

-   -   contacting said first steviol glycoside with a recombinant host        of the disclosure, a cell free extract derived from such a        recombinant host or an enzyme preparation derived from either        thereof;    -   thereby to convert the first steviol glycoside into the second        steviol glycoside.

In such a method, the second steviol glycoside may be steviol-19-diside,steviolbioside, stevioside,13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester, RebA, RebE, RebD orRebM.

In such a method, the first steviol glycoside may besteviol-13-monoside, steviol-19-monoside, rubusoside, stevioside,Rebaudioside A or 13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester and the secondglycosylated diterpene is steviol-19-diside, steviolbioside, stevioside,13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester, RebA, RebE or RebD.

That is to say, the disclosure relates to a method of bioconversion orbiotransformation.

A steviol glycoside or composition produced by the fermentation processaccording to the present disclosure may be used in any application knownfor such compounds. In particular, they may for instance be used as asweetener, for example in a food or a beverage. According to thedisclosure therefore, there is provided a foodstuff, feed or beveragewhich comprises a steviol glycoside or a composition of the disclosure.

For example a steviol glycoside or a composition of the disclosure maybe formulated in soft drinks, as a tabletop sweetener, chewing gum,dairy product such as yoghurt (eg. plain yoghurt), cake, cereal orcereal-based food, nutraceutical, pharmaceutical, edible gel,confectionery product, cosmetic, toothpastes or other oral cavitycomposition, etc. In addition, a steviol glycoside or a composition ofthe disclosure can be used as a sweetener not only for drinks,foodstuffs, and other products dedicated for human consumption, but alsoin animal feed and fodder with improved characteristics.

Accordingly, the disclosure provides, inter alia, a foodstuff, feed orbeverage which comprises a steviol glycoside prepared according to aprocess of the disclosure.

During the manufacturing of foodstuffs, drinks, pharmaceuticals,cosmetics, table top products, chewing gum the conventional methods suchas mixing, kneading, dissolution, pickling, permeation, percolation,sprinkling, atomizing, infusing and other methods can be used.

A steviol glycoside or a composition of the disclosure can be used indry or liquid forms. It can be added before or after heat treatment offood products. The amount of the sweetener depends on the purpose ofusage. It can be added alone or in the combination with other compounds.

Compounds produced according to the method of the disclosure may beblended with one or more further non-caloric or caloric sweeteners. Suchblending may be used to improve flavour or temporal profile orstability. A wide range of both non-caloric and caloric sweeteners maybe suitable for blending with a steviol glycoside or a composition ofthe disclosure. For example, non-caloric sweeteners such as mogroside,monatin, aspartame, acesulfame salts, cyclamate, sucralose, saccharinsalts or erythritol. Caloric sweeteners suitable for blending with asteviol glycoside or a composition of the disclosure include sugaralcohols and carbohydrates such as sucrose, glucose, fructose and HFCS.Sweet tasting amino acids such as glycine, alanine or serine may also beused.

A steviol glycoside or a composition of the disclosure can be used inthe combination with a sweetener suppressor, such as a natural sweetenersuppressor. It may be combined with an umami taste enhancer, such as anamino acid or a salt thereof.

A steviol glycoside or a composition of the disclosure can be combinedwith a polyol or sugar alcohol, a carbohydrate, a physiologically activesubstance or functional ingredient (for example a carotenoid, dietaryfiber, fatty acid, saponin, antioxidant, nutraceutical, flavonoid,isothiocyanate, phenol, plant sterol or stanol (phytosterols andphytostanols), a polyols, a prebiotic, a probiotic, a phytoestrogen, soyprotein, sulfides/thiols, amino acids, a protein, a vitamin, a mineral,and/or a substance classified based on a health benefits, such ascardiovascular, cholesterol-reducing or anti-inflammatory.

A composition with a steviol glycoside or a composition of thedisclosure may include a flavoring agent, an aroma component, anucleotide, an organic acid, an organic acid salt, an inorganic acid, abitter compound, a protein or protein hydrolyzate, a surfactant, aflavonoid, an astringent compound, a vitamin, a dietary fiber, anantioxidant, a fatty acid and/or a salt.

A steviol glycoside or a composition of the disclosure may be applied asa high intensity sweetener to produce zero calorie, reduced calorie ordiabetic beverages and food products with improved tastecharacteristics. Also it can be used in drinks, foodstuffs,pharmaceuticals, and other products in which sugar cannot be used.

In addition, a steviol glycoside or a composition of the disclosure maybe used as a sweetener not only for drinks, foodstuffs, and otherproducts dedicated for human consumption, but also in animal feed andfodder with improved characteristics.

The examples of products where a steviol glycoside or a composition ofthe disclosure can be used as a sweetening compound can be as alcoholicbeverages such as vodka, wine, beer, liquor, sake, etc; natural juices,refreshing drinks, carbonated soft drinks, diet drinks, zero caloriedrinks, reduced calorie drinks and foods, yogurt drinks, instant juices,instant coffee, powdered types of instant beverages, canned products,syrups, fermented soybean paste, soy sauce, vinegar, dressings,mayonnaise, ketchups, curry, soup, instant bouillon, powdered soy sauce,powdered vinegar, types of biscuits, rice biscuit, crackers, bread,chocolates, caramel, candy, chewing gum, jelly, pudding, preservedfruits and vegetables, fresh cream, jam, marmalade, flower paste,powdered milk, ice cream, sorbet, vegetables and fruits packed inbottles, canned and boiled beans, meat and foods boiled in sweetenedsauce, agricultural vegetable food products, seafood, ham, sausage, fishham, fish sausage, fish paste, deep fried fish products, dried seafoodproducts, frozen food products, preserved seaweed, preserved meat,tobacco, medicinal products, and many others. In principle it can haveunlimited applications.

The sweetened composition comprises a beverage, non-limiting examples ofwhich include non-carbonated and carbonated beverages such as colas,ginger ales, root beers, ciders, fruit-flavored soft drinks (e.g.,citrus-flavored soft drinks such as lemon-lime or orange), powdered softdrinks, and the like; fruit juices originating in fruits or vegetables,fruit juices including squeezed juices or the like, fruit juicescontaining fruit particles, fruit beverages, fruit juice beverages,beverages containing fruit juices, beverages with fruit flavorings,vegetable juices, juices containing vegetables, and mixed juicescontaining fruits and vegetables; sport drinks, energy drinks, nearwater and the like drinks (e.g., water with natural or syntheticflavorants); tea type or favorite type beverages such as coffee, cocoa,black tea, green tea, oolong tea and the like; beverages containing milkcomponents such as milk beverages, coffee containing milk components,cafe au lait, milk tea, fruit milk beverages, drinkable yogurt, lacticacid bacteria beverages or the like; and dairy products.

Generally, the amount of sweetener present in a sweetened compositionvaries widely depending on the particular type of sweetened compositionand its desired sweetness. Those of ordinary skill in the art canreadily discern the appropriate amount of sweetener to put in thesweetened composition.

A steviol glycoside or a composition of the disclosure can be used indry or liquid forms. It can be added before or after heat treatment offood products. The amount of the sweetener depends on the purpose ofusage. It can be added alone or in the combination with other compounds.

During the manufacturing of foodstuffs, drinks, pharmaceuticals,cosmetics, table top products, chewing gum the conventional methods suchas mixing, kneading, dissolution, pickling, permeation, percolation,sprinkling, atomizing, infusing and other methods can be used.

Thus, compositions of the present disclosure can be made by any methodknown to those skilled in the art that provide homogenous even orhomogeneous mixtures of the ingredients. These methods include dryblending, spray drying, agglomeration, wet granulation, compaction,co-crystallization and the like.

In solid form a steviol glycoside or a composition of the disclosure canbe provided to consumers in any form suitable for delivery into thecomestible to be sweetened, including sachets, packets, bulk bags orboxes, cubes, tablets, mists, or dissolvable strips. The composition canbe delivered as a unit dose or in bulk form.

For liquid sweetener systems and compositions convenient ranges offluid, semi-fluid, paste and cream forms, appropriate packing usingappropriate packing material in any shape or form shall be inventedwhich is convenient to carry or dispense or store or transport anycombination containing any of the above sweetener products orcombination of product produced above.

The composition may include various bulking agents, functionalingredients, colorants, flavors.

The terms “sequence homology” or “sequence identity” are usedinterchangeably herein. For the purpose of this disclosure, it isdefined here that in order to determine the percentage of sequencehomology or sequence identity of two amino acid sequences or of twonucleic acid sequences, the sequences are aligned for optimal comparisonpurposes. In order to optimize the alignment between the two sequencesgaps may be introduced in any of the two sequences that are compared.Such alignment can be carried out over the full length of the sequencesbeing compared. Alternatively, the alignment may be carried out over ashorter length, for example over about 20, about 50, about 100 or morenucleic acids/based or amino acids. The sequence identity is thepercentage of identical matches between the two sequences over thereported aligned region.

A comparison of sequences and determination of percentage of sequenceidentity between two sequences can be accomplished using a mathematicalalgorithm. The skilled person will be aware of the fact that severaldifferent computer programs are available to align two sequences anddetermine the identity between two sequences (Kruskal, J. B. (1983) Anoverview of sequence comparison In D. Sankoff and J. B. Kruskal, (ed.),Time warps, string edits and macromolecules: the theory and practice ofsequence comparison, pp. 1-44 Addison Wesley). The percent sequenceidentity between two amino acid sequences or between two nucleotidesequences may be determined using the Needleman and Wunsch algorithm forthe alignment of two sequences. (Needleman, S. B. and Wunsch, C. D.(1970) J. Mol. Biol. 48, 443-453). Both amino acid sequences andnucleotide sequences can be aligned by the algorithm. TheNeedleman-Wunsch algorithm has been implemented in the computer programNEEDLE. For the purpose of this disclosure the NEEDLE program from theEMBOSS package was used (version 2.8.0 or higher, EMBOSS: The EuropeanMolecular Biology Open Software Suite (2000) Rice,P. Longden,I. andBleasby, A. Trends in Genetics 16, (6) pp276-277,http://emboss.bioinformatics.nl/). For protein sequences EBLOSUM62 isused for the substitution matrix. For nucleotide sequence, EDNAFULL isused. The optional parameters used are a gap-open penalty of 10 and agap extension penalty of 0.5. The skilled person will appreciate thatall these different parameters will yield slightly different results butthat the overall percentage identity of two sequences is notsignificantly altered when using different algorithms.

After alignment by the program NEEDLE as described above the percentageof sequence identity between a query sequence and a sequence of thedisclosure is calculated as follows: Number of corresponding positionsin the alignment showing an identical amino acid or identical nucleotidein both sequences divided by the total length of the alignment aftersubtraction of the total number of gaps in the alignment. The identitydefined as herein can be obtained from NEEDLE by using the NOBRIEFoption and is labeled in the output of the program as“longest-identity”.

The nucleic acid and protein sequences of the present disclosure canfurther be used as a “query sequence” to perform a search against publicdatabases to, for example, identify other family members or relatedsequences. Such searches can be performed using the NBLAST and XBLASTprograms (version 2.0) of Altschul, et al. (1990) J. Mol. Biol.215:403-10. BLAST nucleotide searches can be performed with the NBLASTprogram, score=100, wordlength=12 to obtain nucleotide sequenceshomologous to nucleic acid molecules of the disclosure. BLAST proteinsearches can be performed with the XBLAST program, score=50,wordlength=3 to obtain amino acid sequences homologous to proteinmolecules of the disclosure. To obtain gapped alignments for comparisonpurposes, Gapped BLAST can be utilized as described in Altschul et al.,(1997) Nucleic Acids Res. 25(17): 3389-3402. When utilizing BLAST andGapped BLAST programs, the default parameters of the respective programs(e.g., XBLAST and NBLAST) can be used. See the homepage of the NationalCenter for Biotechnology Information at http://www.ncbi.nlm.nih.gov/.

Embodiments According to the Disclosure

-   1. A variant polypeptide having geranylgeranyl pyrophosphate    synthase activity, such as a variant of a reference polypeptide    having geranylgeranyl pyrophosphate synthase activity, which variant    polypeptide comprises an amino acid sequence which, when aligned    with a geranylgeranyl pyrophosphate synthase comprising the sequence    set out in SEQ ID NO: 1, comprises at least one modification,    preferably at least one substitution, of an amino acid residue    corresponding to any of amino acids at positions-   92, 100 or 235

said positions being defined with reference to SEQ ID NO: 1 and whereinthe variant has one or more modified properties as compared with areference polypeptide having geranylgeranyl pyrophosphate synthaseactivity.

-   2. A variant polypeptide according to embodiment 1, wherein the    modified property is modified geranylgeranyl pyrophosphate synthase    activity.-   3. A variant polypeptide according to embodiment 1 or 2, wherein the    reference polypeptide comprises the geranylgeranyl pyrophosphate    synthase of SEQ ID NO: 1 or SEQ ID NO: 17.-   4. A variant polypeptide according to any one of the preceding    embodiments, wherein said variant comprises an amino acid sequence    which, when aligned with a geranylgeranyl pyrophosphate synthase    comprising the sequence set out in SEQ ID NO: 1, comprises a    substitution of the amino acid residue corresponding to amino acid    at position 92 with an amino acid residue selected from a Glu    residue, an Asp residue, an Asn residue, a Gln residue, preferably a    Glu residue, said positions being defined with reference to SEQ ID    NO: 1 and wherein the variant has one or more modified properties as    compared with a reference polypeptide having geranylgeranyl    pyrophosphate synthase activity.-   5. A variant polypeptide according to any one of the preceding    embodiments, wherein said variant comprises an amino acid sequence    which, when aligned with a geranylgeranyl pyrophosphate synthase    comprising the sequence set out in SEQ ID NO: 1, comprises a    substitution of the amino acid residue corresponding to amino acid    at position 100 with an amino acid residue selected from a Val    residue, a Gly residue, a Phe residue, a Tyr residue, a Ile residue,    a Leu residue, preferably a Val residue, said positions being    defined with reference to SEQ ID NO: 1 and wherein the variant has    one or more modified properties as compared with a reference    polypeptide having geranylgeranyl pyrophosphate synthase activity.-   6. A variant polypeptide according to any one of the preceding    embodiments, wherein said variant comprises an amino acid sequence    which, when aligned with a geranylgeranyl pyrophosphate synthase    comprising the sequence set out in SEQ ID NO: 1, comprises a    substitution of the amino acid residue corresponding to amino acid    at position 235 with an amino acid residue selected from a Asn    residue, a Ala residue, a Gly residue, a Gln residue, a Val residue,    a Asp residue, a Glu residue, a Phe residue, a Tyr residue,    preferably a Asn residue, said positions being defined with    reference to SEQ ID NO: 1 and wherein the variant has one or more    modified properties as compared with a reference polypeptide having    geranylgeranyl pyrophosphate synthase activity.-   7. A variant polypeptide according to any one of the preceding    embodiments, wherein the variant polypeptide is a non-naturally    occurring polypeptide.-   8. A variant polypeptide according to any one of the preceding    embodiments which comprises additional substitutions other than    those defined in embodiment 1.-   9. A variant polypeptide according to any one of the preceding    embodiments having at least 70%, at least 75%, at least 80%, at    least 85%, at least 90%, at least 95%, at least 97%, at least 98% or    at least 99% sequence identity with SEQ ID NO: 1 or SEQ ID NO: 17.-   10. A variant polypeptide having geranylgeranyl pyrophosphate    synthase activity comprising an amino acid sequence having at least    about 95% sequence identity, at least 96%, at least 97%, at least    98% or at least 99% sequence identity to any one of SEQ ID NOs: 3,    5, 7, 9, 11, 13, 15, 18 to 33.-   11. A variant polypeptide having geranylgeranyl pyrophosphate    synthase activity wherein said polypeptide catalyzes one or more of    the following reactions:    -   dimethylallyl diphosphate+isopentenyl        diphosphate=diphosphate+geranyl diphosphate;    -   geranyl diphosphate+isopentenyl        diphosphate=diphosphate+(2E,6E)-farnesyl diphosphate;    -   (2E,6E)-farnesyl diphosphate+isopentenyl        diphosphate=diphosphate+geranylgeranyl diphosphate.-   12. A polynucleotide comprising a sequence encoding a variant    polypeptide according to any one of the preceding embodiments.-   13. A nucleic acid construct comprising the polynucleotide sequence    of embodiment 12, operably linked to one or more control sequences    capable of directing the expression of a geranylgeranyl    pyrophosphate synthase in a suitable expression host.-   14. An expression vector comprising a polynucleotide according to    embodiment 12 or a nucleic acid construct according to embodiment    13.-   15. A recombinant host comprising a polynucleotide according to    embodiment 12, a nucleic acid construct according to embodiment 13    or an expression vector according to embodiment 14.-   16. A recombinant host according to embodiment 15 which is capable    of producing steviol or a steviol glycoside.-   17. A recombinant host according to embodiment 15 or 16 which    comprises one or more recombinant nucleotide sequence(s) encoding:

a polypeptide having ent-copalyl pyrophosphate synthase activity;

a polypeptide having ent-Kaurene synthase activity;

a polypeptide having ent-Kaurene oxidase activity; and

a polypeptide having kaurenoic acid 13-hydroxylase activity.

-   18. A recombinant host according to any one of embodiments 15 to 17,    which comprises a recombinant nucleic acid sequence encoding a    polypeptide having NADPH-cytochrome p450 reductase activity.-   19. A recombinant host according to any one of embodiments 15 to 18    which comprises a recombinant nucleic acid sequence encoding one or    more of:

(i) a polypeptide having UGT74G1 activity;

(ii) a polypeptide having UGT2 activity;

(iii) a polypeptide having UGT85C2 activity; and

(iv) a polypeptide having UGT76G1 activity.

-   20. A recombinant host according to any one of embodiments 15 to 19,    wherein the host belongs to one of the genera Saccharomyces,    Aspergillus, Pichia, Kluyveromyces, Candida, Hansenula, Humicola,    Issatchenkia, Trichosporon, Brettanomyces, Pachysolen, Yarrowia,    Yamadazyma or Escherichia.-   21. A recombinant host according to embodiment 20, wherein the    recombinant host is a Saccharomyces cerevisiae cell, a Yarrowia    lipolytica cell, a Candida krusei cell, an lssatchenkia orientalis    cell or an Escherichia coli cell.-   22. A recombinant host according to any one of embodiments 15 to 21,    wherein the ability of the host to produce geranylgeranyl    diphosphate (GGPP) is upregulated.-   23. A recombinant host according to any one of embodiments 15 to 22    which comprises a nucleic acid sequence encoding one or more of:

a polypeptide having hydroxymethylglutaryl-CoA reductase activity;

a polypeptide having farnesyl-pyrophosphate synthetase activity; or,optionally

a polypeptide having geranylgeranyl diphosphate synthase activity whichis different

from a variant polypeptide according to any one of embodiments 1 to 7.

-   24. A process for the preparation of steviol or a steviol glycoside    which comprises fermenting a recombinant host according to any one    of embodiments 15 to 23 in a suitable fermentation medium and,    optionally, recovering the steviol or steviol glycoside.-   25. A process according to any one of embodiment 24 for the    preparation of a steviol glycoside, wherein the process is carried    out on an industrial scale.-   26. A fermentation broth comprising a steviol glycoside obtainable    by the process according to embodiment 24 or 25.-   27. A steviol glycoside obtained by a process according to    embodiment 24 or 25 or obtained from a fermentation broth according    to embodiment 26.-   28. A composition comprising two or more steviol glycosides obtained    by a process according to embodiment 24 or 25 or obtained from a    fermentation broth according to embodiment 26.-   29. A foodstuff, feed or beverage which comprises a steviol    glycoside according to embodiment 27 or a composition according to    embodiment 28.-   30. A method for converting a first steviol glycoside into a second    steviol glycoside, which method comprises:    -   contacting said first steviol glycoside with a recombinant host        according to any one of embodiments 15 to 23, a cell free        extract derived from such a recombinant host or an enzyme        preparation derived from either thereof;    -   thereby to convert the first steviol glycoside into the second        steviol glycoside.-   31. A method according to embodiment 30, wherein the second steviol    glycoside is: steviol-19-diside, steviolbioside, stevioside,    13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid    2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester, RebA, RebE, RebD or    RebM.-   32. A method according to embodiment 31, wherein the first    glycosylated diterpene is steviol-13-monoside, steviol-19-monoside,    rubusoside, stevioside, Rebaudioside A or    13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid    2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester and the second    glycosylated diterpene is steviol-19-diside, steviolbioside,    stevioside, 13-[(β-D-Glucopyranosyl)oxy)kaur-16-en-18-oic acid    2-O-β-D-glucopyranosyl-β-D-glucopyranosyl ester, RebA, RebE or RebD.-   33. A method for producing a geranylgeranyl pyrophosphate synthase    comprising cultivating a host cell according to embodiment 15 under    conditions suitable for production of the geranylgeranyl    pyrophosphate synthase and, optionally, recovering the    geranylgeranyl pyrophosphate synthase.-   34. A method for producing a GGPS polypeptide variant according to    any one of embodiments 1 to 14, which method comprises:    -   a) selecting a reference GGPS polypeptide;    -   b) substituting at least one amino acid residue corresponding to        any of 92, 100 or 235        -   said positions being defined with reference to SEQ ID NO: 1;    -   c) optionally substituting one or more further amino acids as        defined in b);    -   d) preparing the variant resulting from steps a)-c);    -   e) determining a property of the variant, for example as set out        in the Examples; and    -   f) selecting a variant with an altered property in comparison to        the reference GGPS polypeptide.-   35. A method according to embodiment 34 wherein the reference GGPS    polypeptide has the sequence set out in SEQ ID NO: 1.

A reference herein to a patent document or other matter which is givenas prior art is not to be taken as an admission that that document ormatter was known or that the information it contains was part of thecommon general knowledge as of at the priority date of any of theclaims.

The disclosure of each reference set forth herein is incorporated hereinby reference in its entirety.

The present disclosure is further illustrated by the following Examples:

EXAMPLES General

Standard genetic techniques, such as overexpression of enzymes in thehost cells, as well as for additional genetic modification of hostcells, are known methods in the art, such as described in Sambrook andRussel (2001) “Molecular Cloning: A Laboratory Manual (3^(rd) edition),Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, orF. Ausubel et al, eds., “Current protocols in molecular biology”, GreenPublishing and Wiley Interscience, New York (1987). Methods fortransformation and genetic modification of fungal host cells are knownfrom e.g. EP-A-0 635 574, WO 98/46772, WO 99/60102 and WO 00/37671.

Example 1 Geranyloeranyl Pyrophosphate Synthase Enzymes

Gene variants of GGS (see table 2 below) were ordered as syntheticconstructs. These were assembled to expression cassettes containing astrong constitutive promoter, the GGS gene, and a terminator by usingtype II restriction enzymes. Similarly, expression cassettes wereconstructed for HYG (encoding for resistance against hygromycin).Integration flanks that allow homologous recombination in Y. lipolyticawere also constructed. These integration flanks are referred to as5′INT3 and 3′INT3. The different parts contain homologous sequences of50 bp to allow assembly through homologous recombination in S.cerevisiae. These parts, together with a linearized pRS417 destinationvector also containing two 50 bp homologous sequences were transformedto S. cerevisiae. Upon assembly in S. cerevisiae, the expression pathwayconsists of 3′ INT3, GGS expression cassette, HYG expression cassette,5′ INT3.

TABLE 2 GGS gene variants Name Description SEQ ID NO Yl_GGS.orf_0001Yarrowia GGS SEQ ID NO: 1 Yl_GGS.orf_0002 Yarrowia GGS with SEQ ID NO: 3Gly92Glu mutation Yl_GGS.orf_0003 Yarrowia GGS with SEQ ID NO: 5Ala100Val mutation Yl_GGS.orf_0004 Yarrowia GGS with SEQ ID NO: 7Ser235Asn mutation Yl_GGS.orf_0005 Yarrowia GGS with SEQ ID NO: 9Gly92Glu + Ala100Val mutation Yl_GGS.orf_0006 Yarrowia GGS with SEQ IDNO: 11 Gly92Glu + Ser235Asn mutation Yl_GGS.orf_0007 Yarrowia GGS withSEQ ID NO: 13 Ala100Val + Ser235Asn mutation Yl_GGS.orf_0008 YarrowiaGGS with SEQ ID NO: 15 Gly92Glu + Ala100Val + Ser235Asn mutation

All GGS ORFs were optimized for expression in Yarrowia by removing rarecodons.

The plasmid containing the expression pathway was isolated from S.cerevisiae and the expression pathway was PCR-amplified. The purifiedPCR products were transformed to Y. lipolytica strain ML15186. ML15186was also transformed with the HYG expression cassette only. The ML15186strain already has all the elements to produce steviol glycosides andkaurenoic acid (KA)-glycosides. The construction of this strain isdescribed in International patent application no. PCT/EP2016/058882(published as WO2016/170045 A1).

Example 2 Production of Alvcosvlated Kaurenoic Acid and SteviolAlvcosides

ML15186 transformed with the different GGS variants and with HYG only asa control were plated on YPhD plates containing hygromycin. Singlecolony isolates were obtained, and a production test was performed: aspre-culture 200 μl YEP with glucose was inoculated with colony materialfrom YEPh-D agar plates containing hygromycin. Nine replicate cultureswere used per GGS variant and 46 for the HYG control. The pre-culturewas incubated 48 hours in an Infors incubator at 30° C., 750 rpm and 80%humidity. 40 μI of pre-culture was used to inoculate 2.5 ml mineralmedium with glucose as carbon source. These production cultures wereincubated 120 hours in an Infors incubator at 30° C., 500 rpm, 80%humidity. The production cultures were pelleted by centrifugation at2750 xg for 10 minutes. After centrifugation supernatant was transferredand diluted in 33% acetonitrile and analyzed using LC/MS for steviolglycosides and related products. The major products were RebA, RebB,Stevioside, Rubusoside, Steviol-19-MS and (mono-, di- and tri-)glycosylated kaurenoic acid. The sum of the production levels (on molarbasis) for each GGS design were normalized and listed in Table 3.

TABLE 3 Production of steviol glycosides and KA-glycosides in strainsexpressing geranylgeranyl pyrophosphate synthase enzymes Normalizedproduction of steviol- and KA- name Description glycosides No extra GGSHYG only control 1.0 Yl_GGS.orf_0001 Yarrowia GGS 1.0 Yl_GGS.orf_0002Yarrowia GGS with Gly92Glu 1.4 mutation Yl_GGS.orf_0003 Yarrowia GGSwith Ala100Val 1.6 mutation Yl_GGS.orf_0004 Yarrowia GGS with Ser235Asn1.3 mutation Yl_GGS.orf_0005 Yarrowia GGS with Gly92Glu + 1.9 Ala100Valmutation Yl_GGS.orf_0006 Yarrowia GGS with Gly92Glu + 1.4 Ser235Asnmutation Yl_GGS.orf_0007 Yarrowia GGS with Ala100Val + 1.8 Ser235Asnmutation Yl_GGS.orf_0008 Yarrowia GGS with Gly92Glu + 1.7 Ala100Val +Ser235Asn mutation

We found that the transformants that had the GGS variants 0002 to 0008expressed (SEQ ID NOs: 3, 5, 7, 9, 11, 13 and 15), producedsignificantly higher titers of steviol glycosides and KA-glycosidescompared to the controls (HYG only and GGS wild type, SEQ ID NO: 1). AllGGS variants (SEQ ID Nos: 3, 5, 7, 9, 11, 13 and 15) were significantlybetter compared to the wild type (SEQ ID NO: 1), with a False DiscoveryRate below 0.0005.

In conclusion, we found that merely adding another copy of the wild-typeGGS (SEQ ID NO: 1) did not improve production, whereas adding one of thevariants (SEQ ID Nos: 3, 5, 7, 9, 11, 13 and 15) improved steviolglycoside and KA-glycoside production significantly.

1. A variant polypeptide having geranylgeranyl pyrophosphate synthaseactivity, which variant polypeptide comprises an amino acid sequencewhich, when aligned with a geranylgeranyl pyrophosphate synthasecomprising the sequence set out in SEQ ID NO: 1, comprises at least onesubstitution of an amino acid residue corresponding to any of aminoacids at positions 92, 100 or 235 said positions being defined withreference to SEQ ID NO: 1 and wherein the variant has one or moremodified properties as compared with a reference polypeptide havinggeranylgeranyl pyrophosphate synthase activity.
 2. A variant polypeptideaccording to claim 1, wherein the modified property is modifiedgeranylgeranyl pyrophosphate synthase activity.
 3. A variant polypeptideaccording to claim 1, wherein the reference polypeptide comprises thegeranylgeranyl pyrophosphate synthase of SEQ ID NO: 1 or SEQ ID NO: 17.4. A variant polypeptide according to claim 1, wherein the variantpolypeptide is a non-naturally occurring polypeptide.
 5. A variantpolypeptide according to claim 1, which comprises additionalsubstitutions other than 92, 100 or
 235. 6. A variant polypeptideaccording to claim 1, having at least 70%, at least 75%, at least 80%,at least 85%, at least 90%, at least 95%, at least 97%, at least 98% orat least 99% sequence identity with SEQ ID NO: 1 or SEQ ID NO:
 17. 7. Avariant polypeptide having geranylgeranyl pyrophosphate synthaseactivity comprising an amino acid sequence having at least about 95%sequence identity, at least 96%, at least 97%, at least 98% or at least99% sequence identity to any one of SEQ ID NOs: 3, 5, 7, 9, 11, 13, 15,18 to
 33. 8. A polynucleotide comprising a sequence encoding apolypeptide according to claim
 1. 9. A nucleic acid construct,optionally an expression vector, comprising the polynucleotide sequenceof claim 8, operably linked to one or more control sequences capable ofdirecting the expression of a geranylgeranyl pyrophosphate synthase in asuitable expression host.
 10. A recombinant host, optionally arecombinant host capable of producing steviol or a steviol glycoside,comprising a polynucleotide according to claim 8 or a nucleic acidconstruct comprising said polynucleotide.
 11. A recombinant hostaccording to claim 10 which comprises one or more recombinant nucleotidesequence(s) encoding: a polypeptide having ent-copalyl pyrophosphatesynthase activity; a polypeptide having ent-Kaurene synthase activity; apolypeptide having ent-Kaurene oxidase activity; and a polypeptidehaving kaurenoic acid 13-hydroxylase activity.
 12. A recombinant hostaccording to claim 10, which comprises a recombinant nucleic acidsequence encoding a polypeptide having NADPH-cytochrome p450 reductaseactivity.
 13. A recombinant host according to claim 10, which comprisesa recombinant nucleic acid sequence encoding one or more of: (i) apolypeptide having UGT74G1 activity; (ii) a polypeptide having UGT2activity; (iii) a polypeptide having UGT85C2 activity; and (iv) apolypeptide having UGT76G1 activity.
 14. A recombinant host according toclaim 10, wherein the host belongs to one of the genera Saccharomyces,Aspergillus, Pichia, Kluyveromyces, Candida, Hansenula, Humicola,Issatchenkia, Trichosporon, Brettanomyces, Pachysolen, Yarrowia,Yamadazyma or Escherichia.
 15. A recombinant host according to claim 10,wherein an ability of the host to produce geranylgeranyl diphosphate(GGPP) is upregulated.
 16. A process for the preparation of steviol or asteviol glycoside which comprises fermenting a recombinant hostaccording to claim 10, in a suitable fermentation medium and,optionally, recovering the steviol or steviol glycoside.